As a beginner, I would recommend you buy an extract kit such as an amber ale of moderate bitterness, perhaps low 30s IBU.
Buy fresh pumpkin, made for eating/baking, and not jack o'lanterns. Carve it up in hand-sized pieces with rind still on. Put on cookie sheet, sprinkle brown sugar over and bake 325F for >30 mins until it looks done.
Cool, cut meat off rind. You can do all that in advance, of course. Or buy Libby canned pumpkin.
Put meat into boil: I've seen everything from 60 mins to 30 mins.
Pumpkin pie spice is available from stores. 1-3 tbs near end of boil should do. I would not add any hops after 30 mins or it will compete with the spices.
Everything, esp. spicing, is variable depending on the beer kit and batch size; you want a nice balance between beer and pumpkin. Good luck.