There are several ways you can say this. It also depends on the relationship between you and the person you are trying to set up a meeting with.
I am going to assume you are asking this by email. Perhaps the two most important things to mention in your email are the reason you are requesting a meeting and the time (and place) you are available.
Here is an example. Note that these are just my words that I came up with now; I may or may not use them when I am about to send an email. The takeaway from this should be "what are the things I need to include in the email".
Hello Count,
You can use any salutation that is appropriate for the relationship between the two of you (you said you know this person). If I am emailing one of my professors at the university, I would go with "Hi Dr. Dracula," or "Good evening Dr. Dracula,".
Hope you are well.
This is optional. Some might advise against it. I personally like to use something like that if I care about the person.
I was wondering if you have some time to meet this week. I would like to discuss (or talk about) ...
Clearly state the reason you want to meet.Clearly state the reason you want to meet.
If possible, be specific. "I have something to say" and "I needed to talk about something" does not work. You don't have to be too specific though.
Try not to be vague: "I would like to talk about my paper." ❌
Try not to be too specific: "I would like to talk about the two-stage least squares regression equations and the negative and statistically insignificant coefficient of the daylight variable." ❌
This is fine: "I would like to talk about some problems I am facing in my data analysis section." ✅
I am available from 5:30 a.m. to 5:30 p.m. on Monday and Wednesday, and from ... on Thursday and Friday. I can meet you in your dungeon if you would like, or we can meet in the computer lab.
If you are not available during these times, or if you wish to meet elsewhere, please suggest what works best for you.
Let them know when you are available.
This is very important. The best thing is to let them know when you are available. Be flexible when you tell them about your availability. And remember to ask them for their preference. If you are always available at a particular time, then it should be "Mondays and Wednesdays" and so on.
If there are arrangements you need to make for the meeting, then you can ask them for a reply or confirmation (so that you have enough time to get things done).