Q: Airport Connection Settings (2 extremes + 1 express)

So recently my settings have gone haywire and I had to default everything.  Since trying to set these connects back up my internet has been terribly slow.  Here is the basic set up:

One extreme is downstairs connected to router providing internet.

One extreme is upstairs which is connected via ethernet to the first extreme

One express in my room.

Im confused as to what the settings should be for each extreme/express (aka extend or create own wireless?)  -- Im pretty new to this kinda stuff, so any help would be appreciated.