Hi @LauraJ
When you install ENS a tool called "SYSPREP" is executed. This checks the system for any potential injectors. If these are injectors which have valid certificates, these are automatically extracted and placed into the Trust Store (which you see via the ENS Common policy). Within the policy you can then specifically select to "Allow" these certificates.
I would advise you to read the following KB - appreciate it is long but it explains the whole process in detail. It also advises you on how to add any certificates manually if needed: https://kc.mcafee.com/agent/index?page=content&id=KB88085