From the TFL website:- Barclays Cycle Hire
At the docking station terminal, online or by phone
For 24 hours or a week
For up to three other family members and friends aged 14 or over. You will all have the same access period
If someone else paid for your access, they’ll need to be with you if you want to hire another cycle during that access period
If you’re a Member and want to buy Casual User access, you’ll need to use a different payment card, to the one registered to your account
Hope this is of use.