Resources to make 8-bit computer like this one?
I'd recommend beginning with reading up on logic gates and binary. Challenge yourself to create a full binary adder circuit and a binary decoder circuit to start with. You can use a simple online logic simulator to begin with such as logic.ly or circuitlab.com - please note that these do not support saving so after your first experiments it may be a good idea to move on to a different simulation software.

There are plentiful resources online to begin learnining about logic ciruits, and soon you'll be able to create more complex and cool things. It's key to learn about things like SR latches and JK flip flops.

Once you've taught yourself a bit of the logic theory, you can start experimenting with physically building them! Get hold of some logic chips and see if you can use a breadboard to create the logic circuits you simulated and learnt about. Use buttons as inputs and LEDs as your outputs.

Most of all, there can be a few 'dry' parts about learning about digital logic however the overall experience can be very satisfying and enjoyable. Have fun with it!