Since you link SFML statically, you also have to link all of SFML's dependencies.
See the
official tutorial for more info.
You could also use the
imgui-sfml branch of the SFML CMake template.
Learning how to use the tools is part of learning how to program. It's normal and expected to take some time.
It can help to do things one step at a time, e.g. just learning how to use SFML first and then think about adding ImGui, or even one step back, learning how libraries work in general and work your way up from there.