It is quite likely that all the certificates you need are installed on your computer system already. You can use EEcerts to check your certificate stores and show all the certificates present: see To display certificate information below.
If you do not have all the certificates required for a job, you must source and install the missing ones. These are usually sent as email attachments – see also Encryption notes. When you double-click the new certificate file, your computer system will open a dialog to import the certificate and install it in its certificate store. (Locking certificates away where your regular file manager can't access them is all part of the security measures.)
Firstly, in EscapeE:
The center panel shows a table of all the certificates in the highlighted store. Just click a different store to view the certificates contained within it.
Clicking a row in the table displays a summary of that certificate's properties in the lower panel; a key icon indicates that you have a private key that corresponds to the certificate. If there is a profile which currently uses the certificate, it is highlighted in the 'Profiles' panel on the right.
To see the full specification of the certificate, click the Details button.