If you pay for Plus and want to cover more groups, open You → Plans & billing and choose Upgrade to Together. Review the price and timing shown by the App Store or Google Play before confirming.
Together replaces your Plus subscription in that store; it does not add five groups on top of a separate Plus allowance. You can cover up to five groups in total. After the purchase, use Your slots and Add a group on the same screen to choose the other groups.
Plus covers one group and cannot be moved to another while it is active. Together is the option for covering several groups you belong to.
If you later switch to Plus through the store, only one group stays covered. The other groups keep their coverage until the current period ends, then return to Free. Check Plans & billing after any change to see the coverage and dates for your groups.