Cannot connect to internet

I have a MacBook Air I bought earlier this year. We only use it when we make a trip while at home we use our iMac Intel. Up to recently I have had no problem connecting to the net with the Mac Book Air but all of a sudden I am not able to do so. We use the iMac Intel as the wi-fi source (I guess through Airport). I am not at all well versed in computer lingo and have seen the long discussion going on presently with this similar problem but understand little of it.

Is there anything I can do to correrct this problem? Thanks.