If the organizer of the event has enabled meetings, you will be able to do so by following the below steps:
To book a meeting with a person, you just need to:
1) Go to a person's profile, by going to the list of participants:
2) Click on one of the proposed meeting slots. If you want to see other slots, click on see more slots.
Note: Meeting slot times are defined by the organizer. They decide from what times meetings between attendees can occur, with whom and for how long.
3) After selecting a slot, choose a meeting place and write a message to the person you want to meet. Once done, click on "send meeting request."
A pending meeting is blocking a meeting slot. If your meeting is not confirmed or refused after a few days, do not hesitate to cancel it in order to free the blocked meeting slot. If you want to make a change to the time or location of the meeting, you will need to cancel the existing meeting and send a new request.
See also: How to book a meeting with an exhibitor?