How do I request forward movement during an interview when I have a job offer from another place?

For clarification:

So, I've been interviewing for a while with no such luck. About a week ago, I had a phone interview with a great company. I did my research on them, including Glassdoor, and I really like their vision and the benefits they offer. The job pays a little less than what I left my old company with, but that's okay because the environment seems awesome.

Yesterday, I interviewed in person with another company while waiting for the first company to call me for an in-person. While the job there is tailored more to what I know how to do, the company is apparently toxic according to almost every review on Glassdoor. These were not "Oh, they didn't let me talk on the phone," kind of complains, these were "There's no work/life balance, they are always laying off, I've been warned about this place, stay away!" etc.

I just received a call from Company B. They already want to offer me a job. I have an in person interview with Company A on Monday. The person from Company B said they'd like to hear my acceptance (or refusal) by Monday or Tuesday.

If the interview with Company A goes well, I want to kind of let them know, "Hey, I have an offer, but I really love your company. What can we do about this?" How do I go about this while sounding professional and not pushy?

Also I'd like to add: I've been unemployed for 8 months since moving to a new state. If I have to take Company B's offer, I definitely will. But I'd really rather go with Company A.