Hi there, looks like a decent wee kit. I can't tell from the listing what kind of motors they are though, it says simply 4401.
If that 4401 indicates nema-17hs4401 like these https://www.cytron.io/p-nema-17hs4401-bipolar-stepper-motor then they're 1.7A each, which means that your power supply would need to supply 4x 1.7A at full power. In reality that would be if you're running four motors simultaneously - which never really happens.
A polargraph-like machine only needs two motors, and the load is small, which is why the motors you'll usually see with polargraphs can be smaller.
An XY machine like you want to make will require more power generally but still usually only two steppers at a time. A "proper" CNC machine or a 3D printer will usually require three or four motors.
For two motors, I'd aim for at least a 2 amp supply and maybe more, but it really depends on what you intend to do with it.
You'll probably be better off looking up more general-purpose drawbot forums, that are focussed on XY platforms like the axidraw. The drawingbots discord channel is a really good place to start: https://discord.gg/fW37yC