There is no doubt that gmail website would be the best place for searching the solution.
I summarize how I handled this problem (ofcourse using gmail help) in following steps:
1.Click “Settings” on the top right corner of your gmail account's homepage
2.Select the Tab “Forwarding and POP/IMAP “
3.There exists two different possibilities two choose : "POP"and "IMAP"(I clicked on the “learn more” of IMAP and found out that gmail has recommended it so I enabled IMAP).
4. Configure your outlook easily without being bothered with the Error prompt this time;)