You can keep them in your inventory
In Sims 3 for PC you go to your inventory and click on the phone were you will get services as an option.
go get a book and look it should be located in the in the case of Sims 3
if it is something you can drag, then open your sims inventory, then roll over the item. if it has a hand, then click and darg. if not, you can't drag it.
Buy an apple from the supermarket and then it will be in the sims inventory, click on it and there will be an option to 'eat'.
It will be in the sim's inventory.
You go to your family inventory
Usually in your inventory
clear your inventory to fix it
You go to there inventory and click on the phone. Then you click on the move option.
Drag the guitar in to your Sims inventory then send them to the park press on the guitar and there you go:)
You have to have the Sims: World Adventures.