Reward points are earnt on every purchase. For each £1 you spend you get 5 points. The reward points are applied to your account manually, so this can take a few days. Each point is worth 1p, so 100 points = £1. You must be logged in to earn and redeem points, but if you register after your order the points can still be applied to your new account.
Reward points can also be earnt by leaving reviews on items you have purchased. Each review earns you 10 points and will be applied to your account manually once the review is processed.