When I try to choose a subclass for a class it will only give me one option for instance with barbarian it will let me choose berserker but not totem or with wizard it will let me choose Evocation but not necromancy or any others can you look into this

Does anyone know how to fix this

Assuming you haven't bought any digital books you'll only have access to the SRD content and the subclasses from it.

You could buy the Players Handbook for the most options upfront but there is a new PHB coming out in September so might be best hold on till then.

If you're creating a character in a campaign with content sharing on, you have access to everything owned by other players in the game.