Welcome to EasyEDA. To start with have you read the forum topic marked **[Must read]**? [https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a](https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a) From there you **must** read (3) in (2) in that linked document. Once you have read that and played with the example sims in it (learning by doing!), you should understand (a) where to find simulatable components and (b) what a net is, and therefore what a ground net is and why it is needed. That said, the spice symbol and model library management is in a state if flux and there are several bugs that have yet to be fixed so here are a few hints and workarounds. 1. There are more models available (from the EasyEDA and the LTspice built-in libraries) than there are symbols in the libraries but we do not have a way to list easily them so if there is a device you want to use, _before_ hunting about the web for a model, post to the forum and ask if it is available; 2. In Sim mode the EElib currently offers a limited number of symbols and therefore models. There are many more Spioce Symbols with models available under the **Spice Symbol > System** tab in the Search Libraries tool;  3. There is also a **Follow** tab which allows you to add Spice Symbols contributed by specific users to the list. Use this with caution because in my experience, most User Contributed Spice Symbols do not work in simulation (for all sorts of reasons because creating symbols with associated models is not hard to do but it is a complicated set of steps that until you get used to it, very often ends in a confusing and ultimately discouraging set of error messages); 4. My primary role in EasyEDA since 2013 has been simulation support so if you follow me then the symbols I have contributed do work (except for those labelled as Do not use" which are ongoing experiments plus a Murata transformer that as yet as no model); 5. The potentiometer in the library was changed some versions ago so if you have a sim more than about a year old you will get an error massage saying there is no model for the pot so replace it with the one from the EELib; 6. This new pot has a bug reported [here.](https://easyeda.com/forum/topic/Simulated-potentiometer-errors-at-and-100-rotation-852c6e27cbb74e33b022778f7fbc3d81) 7. There is a warning message that is bug reported [here](https://easyeda.com/forum/topic/SIM-mode-incorrectly-reports-missing-models-when-they-are-already-in-the-library-873f3fb330e74b08bec474810fe98987) which generates warnings like this:  despite that fact that the LM386EE model is in the library and works fine! If you get that warning, try clicking OK to see if the sim runs before posting for help. If you get a second warning or error message after that then there almost certainly really is a problem in your sim that you need to debug. :)

I too am new to EasyEDA and I too am looking for a concise answer to a simple question. After many searches all I get is countless replies with 'must read blah (2) blah (3) blah. I am trying to simulate a BD139 and a BD140. I have a BD139.LIB and BD1140.LIB from DigiKey. My very very very simple and concise question is what do I do with these in order to get a simulation to work? If this is not a way to ask for help and get an answer then I don't know what is! The error mesage '... please use EELIB and Spice Symbol ...' may mean something to someone who has been using EE for 7 years but does not mean much to me. Many searches on this forum simply lead round in circles to the same couple of documents. Thanks, Andy.

The instruction is to read (3) in (2) in:  [https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a](https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a) which takes you to this document: [Simulation Tutorial](https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub) Reading that document explains what is meant by the message: '... please use EELIB and Spice Symbol ...' because it explains exactly how and where to find the BD139 and BD140 spice symbols that already exist in the EasyEDA spice symbol library and thus avoid having to understand and carry out the procedures described in detail in the chapters on **[Device models](https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub#h.lvrkkmmigksv)** and **[Schematic symbols: prefixes and pin numbers](https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub#h.pkwqa1)** in the [Simulation Tutorial](https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub) in order to use the two .lib files from Digikey (for which no links or information about whether they are .model or .subckt defined models were given).