I think the posts above have some wonderful advice. I'll just add that going for a walk before you have to leave will help drain some energy. When I first adopted Lily, her anxiety was terrible and she'd scream the whole time we were gone. I exercised her (very long walk!) before we would leave and we'd leave her alone, like someone stated above, for short amounts of time working up.
I also think the "Calming" soft chews by Pet Naturals of Vermont are a tremendous help when I'm going to be gone several hours. I will generally give her one chew about an hour before I leave, take her for a walk and put her in her crate when I leave. I stay for about five minutes getting my things ready etc. I do NOT make a big deal out of leaving (bye bye, be a good girl, etc.), I just very calmly walk out the door (I think its harder on me than her!!) I repeat the same ritual when I come home not getting excited but rather calmly saying "good quiet" and letting her out in a calm manor. She'll be excited to see us of course, but I try to keep that energy outside of the crate.
Keep your patience, never take it personally if she makes a mistake and keep up the routine! She'll get used to it and it will be "no big thing" in no time - and by no time I mean that it will gradually get better over the next few months! She's a puppy after all
Best of luck, keep us posted! xo