Yes! If you know the names of the groups you would like to create, list them in the groups column in your initial spreadsheet upload. Members will then show in your All Member Records, and can be viewed in each group that they were listed in.
If groups are determined after your initial upload, you can upload a new list to sort members into groups. Run a new export from your registration system or use the same CSV you used for the original upload, but paste in the group name(s) in the group columns. If your divisions or sessions are the same, you can simply add a group column, and copy and paste the session/divisions into it. Your member records will not be affected; groups will just be created with the proper members assigned to them.
In this case, most members are in one group, but Cory Deleuier is in two:
Then simply upload the list again. (Click here for instructions on how to add members by spreadsheet)
When you click on the group in the Groups tab, the members will have been added.