On the first day of class, allow your SI Leader to give a 3-5 minute introduction talking about what SI is, and how it can help your students. Allow the students the opportunity to ask the SI Leader questions about what sort of things they can expect from the sessions. Maybe drop a line about how good your SI Leader did in the class and how they're qualified to help you.
For each credit hour of a course, a student should be spending 2-3 hours a week studying and engaging with the material for that course. For example, a 3 credit hour Calculus class, students should be studying 6-9 hours per week. With SI sessions, your students will already be getting 3 of those study and engagement hours a week! SI shouldn't be treated as an additional part of the course for students, rather a "supplement" (see what we did there?) to their learning and understanding of the material.
Below are some examples of how we've reframed SI sessions in order to advertise to all students, and normalizing the use of acdemic support.
Not this
Not an extra part of class…
Not just repeat of class/rehash of lecture…
Not just for students that need help...
Not just for students that want to pass...
But this
but a guided and efficient study time with peers
but a “supplement” ;) to help enhance understanding
but for high achievers
but for students aiming to get a higher GPA