It is important to keep your iPhone OS current. This will ensure your iPhone is protected against any security vulnerabilities and provide enhancements to features.
Check here to see which version of the OS you are running.
To upgrade your iPhone OS follow these steps:
1. Connect your iPhone to your computer using the white cable and select iTunes from your Program menu
2. Choose Check for Update
3. iTunes will check to see if your iPhone is running the latest OS versions. If it is, you don’t need to do anything else. If there is a later version we recommend you complete a backup first.
4. Read through the Release Notice of the software upgrade and accept the prompt to download and install. The download will begin followed by the install. Don’t touch your iPhone while this is occuring, it will automatically restart by itself.