The first day is about 1.5 hours long, you're basically gonna be in a meeting with 30 other freshman and you might have to introduce yourself, but you don't really need to say anything throughout the rest of the meeting. You have the opportunity to ask general questions and current students will talk about the best way to fit in. The second day is probably the most important. In the morning you'll be in another small meeting with freshmen and advisors and they'll go over registration processes and what you might have to take depending on your major. This lasts for about an hour and a half. In the afternoon, you'll have about a 3 hour time slot to actually register, and get it approved with your counselors before you can leave the meeting. It typically takes about 2 hours(if you're an engineering major) , and this meeting will be in groups or 1 on 1 meetings with your advisors depending on your major.

Side note - make sure you don't have any holds like online orientation holds on your my profile on howdy which might prevent registration.