If you have taken part in online activities such as Homes for Wildlife or Big Garden Birdwatch (and you requested that we create a website account for you) you should be able to sign in using those details.
If you have used our online shop you will have an account for that but, unfortunately, your shop account does not yet qualify as a Community account. We are working on merging the two so that you can use the same details on both sites.
If you are unsure whether or not you have an account, the best thing to do is to try registering. If you already have an account, the registration page will inform you.