So I recently had a lot of books shared with me by a friend but none of the options are appearing in my character builder. They’re all up to date but I have none of the races, spells and stuff. Is it an actually problem or am I just too stupid?

You must create the character within that specific campaign.

Each player can have up to 99 characters per campaign, so you can make multiple characters in the same campaign and then transfer them out before moving them into another campaign if you need to.

Like I said, once the character has been created you can move it out of the campaign, the shared content already on that character will continue to function. It helps because each person with a Master Tier sub can only share with 5 campaigns max, so it reduces the number of campaigns that require sharing.