Select the tracks. Click the Expose Copper  button. The easiest way to explain about using  vias to increase current carrying capacity is like this: Vias are only helpful if they are filled otherwise the hole takes away more copper than the via through plating adds. Vias in EasyEDA are covered in solder mask anyway and the is no option to uncover them so they will not fill. Pads are not covered. If you want to use the idea of vias then create and place small pads of the same dimensions as the vias you wish to place.

Ok, thank you very much for your reply. ``` But I need to put "Expose cooper" in a copper area. The option of Expose Copper button when I select "Cooper Area" Thank you. ```

You can't do Expose Copper for a Copper Area. Try using the Solid Region tool or use wider tracks.  then the Solid Region will be exposed.

thanks friends, Problem solved. best regards