[Trouble removing the background on 2 pics]

Thanks a bunch!!!! It worked great

[Trouble removing the background on 2 pics]

I am really new to all of this but have read the tutorials over and over again and still can't seem to get it right. I am trying to make a siggy using two pics I have of my dog. I can't remove the background in them without screwing up the whole picture. I really am clueless but trying like heck to learn how to do all of this. Any help would be greatly appreciated!!