There's nothing special about microstrip. It's just a trace on an outer layer over a sufficiently large area of ground plane on another layer. To create a 50 Ohm microstrip you need to know: 1) the dielectric constant of the PCB material between the strip and the ground plane; 2) the thickness of the PCB material between the strip and the ground plane; 3) the thickness of the copper forming the strip. EasyEDA does not provide any microstrip design tools but there are several such tools available online. For example: [http://www.rfcafe.com/references/electrical/microstrip-eq.htm](http://www.rfcafe.com/references/electrical/microstrip-eq.htm) [https://www.pasternack.com/t-calculator-microstrip.aspx](https://www.pasternack.com/t-calculator-microstrip.aspx) [http://chemandy.com/calculators/microstrip-transmission-line-calculator.htm](http://chemandy.com/calculators/microstrip-transmission-line-calculator.htm) You can search the EasyEDA and/or JLCPCB information about the PCB capabilities and standard stack ups for materials dimensions and dielectric constants.