From OCI console, user don't have a option to rename a VCN display name. The method to overcome this is to use the OCI cli command. The fastest way is to use the OCI cloud shell as the OCI CLI is already installed by default.
Open up cloud shell and type in
oci network vcn update --vcn-id XXXXXXX --display-name YYYYY
where XXXXXXX is your VCN OCID and YYYYY is the name you want your VCN display name to change to.
