Since the documentation does not contain any information about how you can connect an existing application to the newly created percona pgo cluster, you can use something like the following in your pod postgresql connection string.

postgresql://username:password@cluster1.pgo-perc-production.svc.cluster.local/production

where cluster1.pgo-perc-production.svc.cluster.local points to your newly created cluster and the /production is the database to connect to.