In Sims 3 for PC you go to your inventory and click on the phone were you will get services as an option.
You can keep them in your inventory
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'.
Usually in your inventory
You go to your family inventory
It will be in the sim's 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:)
Finding the death plant on the Sims 3 and keeping it in your inventory will save you from death. If you have on ein your inventory at the time of your death, you can trade it to the grimreeper for your life back. I'm not sure how much more your Sim can live for as death has never came into my sims life.