The easiest way to input your CPP and OAS income is to use the Find tool in the upper right to search and select each slip - T4A(P) and T4A(OAS).
You can also open the menu on the left side and click the T slips option to see a full list of T slip options.
https://turbotax.community.intuit.ca/community/slips-documents/help/how-do-i-enter-a-t4-slip/00/873472