interfacing custom hardware with device toplevel

Presumed it's compatible with the development board hardware, you can assign the pins of your design in pin planner or assignment editor.

If you are connecting to many pins I/O pins or e.g. memory hardware of the board, it might be convenient to copy the pin assignment of an existing example design. You can either use identical pin names in your design and copy the pin assignment only, or copy the top level design with port definitions.