This document provide you step wise procedure for importing a certificate into portal.
1) Go to the Portal main page
2) Click on SAP NetWeaver Administrator
3) Enter the Portal Admin user id and password
4) Click on configuration Management tab
5) Click on certificates and Keys link
6) Goto Key Storage > Content > Keystore Views
7) Select TicketKeystore entry
8) Click on Import Entry to import from file
9) Provide inputs for Entry type, path of the file and password if it is PKCS#12 Key pair type entry.
10) Click on import to start of file
11) You will be able to see newly added certificate in the list Key Storage View Details