You are going to have to work up to leaving her in the crate for a long period of time and having her be quiet. To get her to walk in on her own throw a few cherrios in the back so she has to go in and get them, let her come back out and a few minutes later try it again. She will soon learn that going in the crate is not so bad.
To break her of the howling/crying habit you first can never let her out of the crate if she is making noise. She needs to know that in order for that door to open she has to be quiet, if you let her out when she is crying/howling she will keep it up until you let her out. Make sure she has lots of comfy blankets in the crate and maybe even something that smells like you. Start with a very small amount of time in the crate like 5 minutes, throw the cherrios in close the door and leave the apartment for 5 minutes. It is important you leave and come back (that is part of the training for her to understand you will come back) Come back and when she is quiet open the door and let her out, don't make a huge deal about leaving or coming home, when you leave say good bye and walk out when you come home open the crate and say hello to her and a few minutes later you can give her all sort of loves. You don't want to make you coming or going a big deal to her, it's just something that happens. An hour or so later leave again for 5 minutes, come home repeat. Lengthen the amount of time you are away when she is quiet when you are away, it might take a while but it will work. YOu might have to train her one weekend, where you can be home and do this all day. It will be worth it in the long run. If you have any questions just ask. Patience is the key. YOu can do it.