The first payment is made just before your Membership starts. The next payment will be made automatically after the chosen period of your Membership (monthly or yearly). So if you, for example, have a monthly membership started on the 26th of januari, the next payment will be done automatically after one month on the 26th of februari.
Depending on your bank it can take a few days to collect te money. During this time your membership could be “On Hold” in your account, but you will keep access to everything, so don’t worry.