To join Club Log, you need to have an invitation from an existing user.
Club Log is a specialised site, designed only for use by real radio amateurs. Attempts to automate the sign up process by bots cause serious inconvenience, so instead you must prove you have an association with the hobby by giving a code that another user issued to you.
They look like this: NDHeXamPlex2
They are 12-characters long, and a mixture of letters and numbers. They are valid only once, and cannot be reused.
If you need an invitation...
Club Log has a very large user base. It's very likely you know someone who can give you an invitation code. Just ask them for a code, and then you can sign up.
Tip: If you do not know any other Club Log users, you can use this form to submit your request to the helpdesk directly: https://clublog.org/requestinvite.php.
If you are asked for an invitation...
Make sure you know the person who is asking for a code. They should be a radio amateur and the holder of a valid transmitting callsign. You will need to be an established Club Log user before you are allowed to issue invite codes.
Go to Settings (top menu) in your Club Log account, and scroll down to "Invite Codes". Cut and paste one of the codes and send it to your friend so they can sign up. If you don't see this option, your account is not yet eligible to issue invitations, sorry.
Note: don't share invite codes on social media or try to re-use them. The codes are single-use only, and you may find you can't create more invitations if you publish them.