You'll need to get yourself to one of two spots for making spells, either work through those mages guild recommendations until you unlock the arcane university altar, or grab yourself the frostcrag spire upgrade for about 3200 gold. Once you're there, the spellmaking process is pretty straightforward but costs can add up quick depending on what you're trying to create.

The system gives you plenty of room to play around with range options like touch or target, and you can adjust things like how strong the spell is or how long it lasts. Something worth keeping in mind, the more powerful you make it the more magicka it'll drain when casting. Combining different effects can lead to some really interesting results, like mixing fire damage with healing or stacking multiple summons together, just remember that bigger spells will hit your gold reserves pretty hard.

Actually works out nice that this hasn't changed from the original version, so if you've done this before you'll feel right at home with the altar mechanics and effect combinations. Just make sure you've learned the effects you want to use first since you can't craft with magic you don't know yet.