Most Helpful Guy
I never heard of losing your data during an update but it may be possible. There are 2 ways to update: with itunes or just from your iphone. First just turn on your wifi on your phon and make sure it is charging so it doesn't lose its charge while updating. 3g is not good use wifi. Go to settings and find the software update button. It should be under about i think depending on your ios version. This will search if your phone can update to the latest ios. U can't choose an ealrier version unless u know how but ts more complicated. The lates ios is 9 i think. it should hav instructions for u to install the new update and just wait fo it to do its thing. It will a bar showing its progress and then shutdown and reboot and will be updated.
Most Helpful Girl
Updating doesn't delete anything from your phone. If anything it will only add things & fix them but you should definitely check the Apple website.