Open up the mission editor, and goto Mission Inspector(f3)
On the tree list to the right side, open up "(number here) Mission group - Sim group"
Then choose "(numberhere) Mission Info - Script object"
open "Dynamic Fields"
Modify these:
Desc0 is the first line of description(caption under preview), IE "Name: Bedroom"
saveName is where the save files are put, IE "Bedroom"
descLines is the number of caption lines, IE "2"
Name is how it shows up on the list, IE "Bedroom"
Desc1 is the second line of description, IE "Author: Eric Hartman"
previewimage is where the Preview is located.
Enjoy.