You can join a Club simply by clicking on the Club symbol:

A window will be shown where you can click on the "Find" button (highlighted by a yellow arrow in the following image)

Then choose teh Club that you like most and click on the "Show" button (see yellow arrow in the following image)

If you like the Club you are browsing then click on the "Enter" button (check yellow arrow)

If you do not like it, click again on the "Find" button and find another Club.