To create a sign-up sheet you can create groups of one (or any other number that relates to the number of students that can sign up for a certain time-slot). You can then name each group in accordance with the chosen date and time of each appointment. Select the group category Self Enrollment. Please visit this page to find more information about creating groups in Brightspace.
You can use Grades to print out an overview of all the appointments (groups). The group title refers to the time slots you've created.