You'll have the option to use them in encounters with other people, or when you masturbate in bed while backpack is equipped (not in the shower, as you're naked in the shower so you don't have your backpack)
Idk if you already found out but if you don't, you can wear some of them (I think only the ones from Utopia euphoria and strap-ons) at the restrooms and you'll have them on until you remove them, and they will function all the time, you just need someone to have the link of your toys or even your character will work on then alone