How to add manually Virtual Server to BIG IP DNS

You should use generic host. Something like below should do, where 1.1.1.1 is the server ip and 443 is the service port. Here basic tcp half open monitor is used. You can tweak accordingly.

create cli transaction
create gtm server 1.1.1.1 addresses add { 1.1.1.1 } datacenter test product generic-host virtual-servers add { 1_1_1_1_443 { destination 1.1.1.1:443 monitor tcp_half_open } }
create gtm pool test-pool members add { 1.1.1.1:1_1_1_1_443}
submit cli transaction