You'll need to specify a VGP in the Compute Resources section of the Resource Set....this is a required field. (https://docs.bmc.com/docs/display/public/clm31/Configuring+compute+resources)
In CLM 3.x you can specify an NSH script or AO workflow in post deployment actions
for compute resources, or as pre/post install actions for software packages.
You can only specify an AO workflow in the Post Deploy Actions tab of the Service Deployment Definition or Resource Set
If specifying a script, it must exist in the CSM_Scripts depot folder. AO workflows must be specified in the format <module>:<name> (https://docs.bmc.com/docs/pages/releaseview.action?pageId=218465891)