Any electrical work in your home needs to have a qualified (preferably licensed) electrician to do the work. It is a dangerous hazard in your home if not done correctly, so we highly recommend that you call a licensed electrician.
When we talk about connecting wires and making connections to electrical wires themselves, you need to make sure they are nice and tight connections. If you have multiple wires coming out of the box and you are trying to connect two wires together at that point, let’s say it is your two black wires. You need to make sure that the insulation is stripped out at least a half inch on the wires to expose the bare copper underneath.
At that point you tie them, you put them side by side, take a pair of pliers, and twist them as much as you can possibly twist them to make sure they are tight enough to not come apart. You can sip the very end off, about an eighth of an inch. Then you can take a wire nut, put it over the wire itself, screw it down as tight as you can. Now you have a connection.