Have a look here: OSOYOO Basic board + CNC Shield V3.0+A4988 Installation Guide « osoyoo.com
There is a schematic for the board. There's also this handy image:

And a lot of other information.
Have a look here: OSOYOO Basic board + CNC Shield V3.0+A4988 Installation Guide « osoyoo.com
There is a schematic for the board. There's also this handy image:

And a lot of other information.