Routers can be very complicated, but they work on simple principles. If we cover the basics and some common problems here, hopefully, you can solve many of the issues we encounter daily. Since different routers have different interfaces, it is impossible to give you specific instructions on making changes.
We'll show you what to do, but I'm afraid it's up to you to figure out how. Your router's manual or support website should have the answers. Generally, I don't particularly appreciate doing non-actionable tutorials, but the sheer variety of routers out there makes it impossible to do so.