Hello,
You have to configure your baselines from SIM internal. This is one of the major changes in SIM 7.x. HP is moving away from the VCA and uses HP SUM for deployment. But for this moment we still use the VCA but you have to configure the baselines in SIM. Here is how. Log into SIM choose Deploy > Software/ Firmware Baselines > Manage Software/Firmware Baselines. If you get a red screen saying that you have to configure a default Version Control Repository select the right option on the same screen to select the VCRM server (most of the time the SIM server). You do need a trust with the VCRM server but that should not be a problem. Now that you have a VCRM selected you should see the Baselines toy uploaded to the VCRM. Now you can choose to add Systems to the baselines that you have.
You can use collections to set the servers to the baselines as long as you selected the servers in the baseline you selected. Click on save, wait one minute to see that the Assigned Systems field gets filled.