It's easy to install just download the appimage from here
https://electrum.org/#downloadAnd then open the folder where the Electrum.appimage right-click the file and go to properties(You need to make it executable to make it work) so you need to enable "Make the file executable" then ok.
Now double click the appimage it should run the Electrum.
If not work, there is another option, you can run Electrum with python you can find the installation guide from the link above under "Installation from Python sources"