If you have access to a dip station with counterweights and/or a lat station (more common) you can start with those and progress until you reach your body weight switching to the regular version of the exercises and even adding weights as you progress to the end of the 5s and beyond.
If you don’t have one or either of those then just keep trying to add reps until you reach the top of the rep range you are in 15s, 10s, 5s. Once you can do more than the top of the rep range then start adding weight to a belt or in a backpack or even hold a DB between your ankles. Keep adding weight every time you exceed the rep range you are in.