How do I unlock an iphone 5?

I have a contract with Tesco mobile which included a phone which I subsequently broke!

Rather than pay for quite an expensive repair, a friend of mine very kindly gave me an iphone 5 they were no longer using.

However, when I put the Tesco mobile sim into the iphone it rejects it.

I'm told I need to unlock the iphone but I have no idea what that means or how to do it.

If anyone could help I would be very grateful!

Try calling apple-care. They should be able to help you. I think.

Before you do anything else, get a Tesco Mobile SIM with a little bit of preloaded credit to check that the phone actually works, and that it's not iCloud locked. If it's iCloud locked, you'll have to get your friend to enter his or her details to unlock it and to then wipe the phone so that you can use it (Settings>General>Reset>Erase All Content And Settings). Wiping the phone blank also requires the last owner to re-enter their Apple ID and Apple Password.

Once you are sure that the phone has been fully reset and ready for you to register it to your own Apple account (you'll be prompted to create one at no cost if you don't already have one), then you can contact Tesco Mobile to ask them to unlock the phone from their network: it's not instant as they have to contact Apple to get the unlocking code and there's a fee involved. Note that if the phone was previously on a Tesco Mobile contract, and if the minimum contract was not completed when the phone was last used, then Tesco might refuse to unlock the phone or may demand additional money to cover the outstanding contract.