Import a external library for my mod

I'm making a mod based on Pixelmon and I would like to get some pixelmon things, like the player's economy, but I don't know how I add the Pixelmon in external libraries in my mod to be able to import pixelmon resources like the economy. I already checked the forum, but I didn't find a solution. I need this for my project, it's essential that I get player economy.