how do you install a toilet?

It's very doable. Turn the water off, flush and sponge out what's left in the tank, disconnect the supply line, then take the nuts off the floor bolts and lift the old one straight up. Scrape every bit of the old wax ring off the flange and check the flange isn't cracked or sitting below the finished floor. If it's low, use an extra thick ring or a spacer. Put the new ring on, line the bolts up through the base and lower the bowl straight down, then press it down with your weight. Don't rock it once it's seated or you break the seal. Tighten the nuts a bit at a time, side to side. Snug, not hard - porcelain cracks. Reconnect, turn on, flush a few times and look for leaks. A lot of people leave the back of the caulk line open so a leak shows up instead of hiding under the floor.