Click on it and read info
I have a question.
info on the landing page link:
Landing pages help you recruit new members to your club by providing a customized home page where they can either sign in or sign up for a new account. Share the page below through a link or a QR code. Once users log in or create a new account, they will not only be directed to your club's page but also automatically added/request to be added to the members list.
To see the customized landing page, make sure you are logged out or open the page in a new incognito
In answer to your 2 questions, I recommend you join these 2 clubs:
Club Admins: https://www.chess.com/club/club-admins
Admin's Corner and Training Club: https://www.chess.com/club/admin-s-corner-and-training-club
These are both informational clubs for club owners and admins. Have a look in the forums when you join. They are both very helpful, and you will find a large amount of resource information for club management, making your admin life much easier. If you still have questions after looking at the resources, ask there and you will get answers from experienced owners & admins.

I own a club called Arena champs and I am a super admin of a club known as House of turtles.
Https://www.chess.com/club/Arena-champs
Https://www.chess.com/club/House-of-Turtles
And I can see one option below the admin settings headline as "Manage Landing Page".
What does it do? Please tell me guys.