You can specify that customers are only allowed to buy a certain membership package if they currently have or have previously purchased another specific membership package. The existing or past membership package is the prerequisite for the new membership package.
Go to Administration > Membership Settings > Packages.
Search for and select the membership package that you want to modify.
Click Change Prerequisites.
Note: Any existing prerequisites for this membership are displayed below the Package section.
In the Prerequisite Group 1 section, select whether the prerequisite needs to be held by the Client Only or by Any Family Member in the client's account.
Choose one or more of the following:
Specify one or more Current Memberships that the customer must have.
To
specify a prerequisite membership to automatically sell when
purchasing the current membership, click the binocular
icon 
for the Immediate
sale Membership box.
Specify one or more package categories that the customer must have a current membership in using the Current Membership in Package Category list.
Specify one or more Past Memberships that the customer must have had at some point in the past.
Specify one or more package categories that the customer must have had a membership in at some point in the past using the Past Membership in Package Category list.
If the prerequisite group includes past membership prerequisites that must have been active within a specific time period in order to be valid, enter the time period in the Time Limit (for Past Membership) section.
To specify another group of prerequisites that customers must satisfy to allow enrollment in the current membership package:
Click Add Prerequisite Group.
Repeat steps 4-6 for the new group.
Note: Use prerequisite groups when you need to create complex systems of prerequisites. If you want to specify that a customer needs only one out of a group of possible prerequisites, put each prerequisite into the same prerequisite group. A customer needs only one of the prerequisites in each prerequisite group in order to fulfil the membership requirement; however, each customer must also satisfy all prerequisite groups.
Click Save.
Note: For complete descriptions of the options on this page, click here.
Adding or modifying a membership package
Adding or modifying a package category