The most common newbie mistake is trapping some tube under the bead.

Start by using the reference line molded into the tire along the rim line, to see where the tire is high or low in the rim.

High spots are almost always trapped tube. You can usually see it if you push he tire away from the rim and look in. The easiest place to free trapped tube is at the valve because you can push the valve in pulling any trapped tube out from under the bead. This is one reason I finish mounts at the valve. Elsewhere freeing trapped tube is harder. You can try dropping the pressure until the tire is limp, then bringing it up slowly to about 5psi and seeing if it pops free when you massage the tire.

Otherwise unmount and remount the tire, ending at the valve, keeping just enough air in the tube to keep it round (bleeding out the air out as you finish makes it easier).

If your tire is low in the rim in some places, which often happens on rims with inside shoulders requires lowering pressure to minimum to keep shape, and massaging the tire toward the low spot and pulling it up by rolling the tire away from the rim at the spot. Sometimes if you get it close, it pops up on it's own as you inflate.

BTW- before mounting, check the tire for any bent bead wire. Straighten it as best you can before mounting.