Welcome to FT
Redeem is when you use miles. You want to claim/earn freq flyer miles
Retro credit of flights to a FFP varies by airline. For many you need to be a signed up member at the date of the flight. However US Airways (at as April 11 2014) allows you credit miles from flights taken 6 months before the date join US dividend miles ffp. US Airways ffp will merge into AA ffp, and is a good ffp for many people
Some information
here but may not be up to date
There are several recent threads on this topic, which I will try to find. Some are
http://www.flyertalk.com/forum/infor...alliances.html
http://www.flyertalk.com/forum/infor...rn-points.html
http://www.flyertalk.com/forum/star-...ill-claim.html
Other threads that may interest you
http://www.flyertalk.com/forum/infor...help-here.html
http://www.flyertalk.com/forum/onewo...help-here.html