Provision Infrastructure in OCI(Oracle Cloud Infrastructure)

I have created scripts which contains 1 VCN, 2 subnets(public and private subnet). I have 1 windows instance( bastion server) in my public subnet and 1 in private subnet.
when i try to connect my private subnet instance from the bastion host for attaching block volume,i am not able to connect, i get connection error. I also opened the network(0.0.0.0/0) but still not able to connect.
i searched it on google also, but i couldn’t find anything.
so if anyone can help,please.