We've seen this expression before on a past blog. Since it's a widely used and idiomatic phrase, we're going to focus on it today. About to + verb means getting ready to do something or something is almost going to happen. For example, you can look up to a cloudy sky and say it's about to rain. When you're stressed out you can say "I'm about to go crazy." If a mother asks her child if he has done his homework, he can reply, "I'm about to do it."
You can use about to with just about any verb.
A: Hi honey! How are the kids?
B: They're driving me insane. I'm about to scream.
A: Alright. Take deep breaths. I'll be home soon. I'm about to leave.
B: That's great. Can you stop by the store for some milk?
A: Sure. You want the organic kind right?
B: Yeah, that'd be great. I might make some milk shakes later. Alright, I'll talk to you later. I'm about to start laundry.
A: Alright. See you later.
just about - almost
driving me - causing me; making me
That's it for today. Use about to as much as you can today. Tomorrow, we'll learn something similar but a little more formal.