You can exchange for your APs at any park ticket window or guest relations location. They should be linked to
MDE automatically during the exchange.
You can purchase a TiW card at any guest relations location. There have been a few reports that guest relations at the International Gateway (back entrance to Epcot) is not selling the TiW card any longer.
AFAIK, Memory Maker is activated by having a photo taken by a PhotoPass photographer. You can stop at one of the camera centers or ask a PhotoPass photographer to find out.