Create dynamic group that matches the instance compartment or instance id:
Any {instance.compartment.id = 'ocid1.compartment.oc1.....'}
Create policy that allows dynamic group to work with autonomous wallet:
Allow dynamic-group <DYNAMIG-GROUP-NAME> to manage autonomous-database-family in compartment <COMPARTMENT-WITH-ATP>
Note: it uses whole database family, more finer policy should be possible to configure, link https://docs.oracle.com/en-us/iaas/Content/Identity/Reference/adbpolicyreference.htm