How do I get my mother to understand she’s in assisted living?

Sounds like she needs some help in the evening to get settled in for sleep. It's not good for you and her to have the evening calls. Ask the AL for ideas, what they have done for other patients, etc. Block her calls if need be. Don't engage with her at this time. Call in the early mornings so you can keep in touch and she has limited time to spend on the phone or ask the AL if this is a good idea.

We told Mom she was in a new apartment. She would have people to talk to and have help. She would ask to go home, I would ignore the comment and change the subject. Believe me I hated being the one she took it out on. My two brothers saw her about 1a yr.

I don't know what to tell you to change your mother's behavior. It is very common with dementia. You can try redirecting her. You can try therapeutic fibs. "They are still working on the sewer line in your street." But that is very difficult behavior to change. I would accept only one call per evening from her at night. Or tell her you will call her every evening at 7:00, so she has something to look forward to (if she can remember). Check caller ID and just don't answer more than one call per evening. The ALF can call you from their phone if there is an emergency.

I also don't know what to tell you to change your own reaction. Your mother's behavior is driven by her dementia. It isn't personal against you. Of course you know that in your head. But, gosh, it still hurts to have your mother yelling abuse at you! Get her out of her room immediately when you visit. If she continues her rant say, "It looks like you are pretty upset today, Mom. I'll leave now and see you on Friday. I hope you are feeling better then." This is not to "teach" your mother to behave (I doubt that is possible) but it is to protect yourself, which is a valid reason to do it.