If you talk to an Enchanter NPC, the option to enchant will be in the dialogue list like a shop owner or spell crafter. Since you’re in the Mages Guild, the easiest to reach would probably be Galbedir in the Balmora Mages Guild.
If you need more specific info the UESP wiki (https://en.uesp.net/wiki/Main_Page) is a great source. Just be weary of spoilers. I personally use it to check racial attribute spreads whenever I start a new game.
Thank you. Will using an NPC to enchant items increase my enchanting skill like in Skyrim?
No, but enchant skill in Morrowind is kinda weird so I honestly wouldn’t worry about leveling it for a first time playthrough. I never leveled it and was still able to enchant some exquisite pants with enough stamina restore to negate fatigue entirely, for example.
