If you want new users to have to select their membership as well as pay for their membership before having an account at your club, you need to require memberships on your club's Sign Up Form.
To require this, we'll go to SETTINGS > PORTAL SETTINGS > SETUP
We'll scroll to Optional Fields:
NOTE: 'Require Membership on Sign Up Form' will require them to select a membership in order to create their account.
If the membership is NOT free, they will have to pay for the membership before their account will be created.
If your club uses approvals for new accounts created, and the account is DENIED, the user will be refunded via their original form of payment.