The license file should be copied to Rainlendar's settings folder (either /home/emichelle/.rainlendar2 or /home/emichelle/.config/.rainlendar2 depending on the Linux distro). The "Install the license..." menu item does this automatically for you.
If Rainlendar's about dialog shows it as the lite version even if you have installed the pro it means that the application cannot load the plugins during the startup. You should get an error about this though when Rainlendar is started.
Try running Rainlendar from the command prompt with the "--debug" argument:
There should be a "Show debug log" item in the context menu which opens the log. Check the log for possible errors (usually in this kind of situation one of the 3rd party libraries are too old in your system).