I recently bought an Anet A8 3D printer. I assembled it, leveled the bed and filled it with fillament. When I try to print, It displays “printing 0%”, slowly going up to 100% but nothing happens. I am not trying to print an stl file, but a gcode that I sliced with cura. Do you have any idea as to what is wrong?

Sounds like you need to check your cables. Is the hot end / bed warming up?
Which profile did you load into cura?

When I select preheat both the extruder and the hotbed warm up. Also, all the motors work fine when I select home all. I used a custom profile as described by this video: