Connection string to Key Vault

Hello guys, i want to save my connection string from postgresql server to key vault secrets…

but im not really sure howv to do that which brings out some questions…

i create postgresql server but i did not create any database there… is it required ? because if yes i should first create virtual server and some vlan and also create database on my postgredb and then i should be able to get my connection string and get it store into my key vault i created right ?