I want to link only specific emails to lead items or case items appropriately, but is that even possible?

Hi everyone
If you know some ways of the subject, could you support me please?

I am not an engeneer but just the use person, I am a sales person.
I would like to see the specific mail in Creatio, but not all of the mail.

How do I can bring it into the Creatio?

Also, I would like to know, what is the logic behind automatically selecting emails that are linked? I believe there are interactions with the same customer in both Opportunity and Lead. How does it automatically determine that? What's the key?

Sorry for all the talk, but I need your help.

Thanks!