Route website through site-to-site VPN

[ppreininger]

Hi,
I'm struggling with a configuration I want to achieve. I have got two sites with a Wireguard Site to site VPN running - works great.
Now comes the part I'm having problems with:
I want to access a certain IP address from site A via site B. I don't know, if what I'm describing is clear. I want to access the certain IP from Site A as if I was accessing it via site B.

Any ideas how to configure that?

Thank you for your help

[errored out]

Quick question, where is the computer that will be accessing this IP? Will the computer be at Site A sending out a connection to site B, then looping back to Site A? Or, will the computer be at Site B connecting to Site A?