help with re installing apps

[xanderyoyo]

hi i was advised by the o2 shop that i needed to reset my i phone and was told that all my apps would not be lost as thay were backed up on my pc

i did this and now it tells me that im not authorized to install them from my computer ???????????????????????????????????????
have i lost £20 worth of apps or am i doing somthing rong ??

[Picazzo]

You're not losing any of your apps! Have you used the backup file from iTunes?

[xanderyoyo]

yes it has put all but the aps back on the phone