What to do after filling a Rainsoft with salt

I'm renting a house and it has a standing Rainsoft water system. I don't know model number and can't source one online. It's a light beige system with a black top. It has a manual timer with several options on it.

I filled it up with salt over the weekend, but its still not filling up with water. From what i've read online it should fill up. Is there something i'm supposed to do after filling it with salt?

Thanks,

Tony