New purchase, brake help!

[Gruman]

Just purchased a '69 C20 with non-working brakes. Has been sitting for 7 years, motor runs now. The reservoir is empty and when I push the brakes, the pedal stays on the floor, doesn't spring back. Previous owner said there was a hole in the brake line somewhere and he has put a screw in it to slow the leak. English was not his first language so that's all the explanation I got. Where should I even start to fix this? Fill the reservoir and see where it leaks out of?

I know almost nothing about brakes so any help here would be appreciated.

Thanks!