Hi Ria,
Go through the below links to understand better:
Master Data Setup for Safety Stock Planning - Master Data for Supply Network Planning - SAP Library
Extended Safety Stock Planning in Capable-to-Match (CTM)
Safety stock planning with CTM | SCN
Also check SAP note
855229 - FAQ : Capable-to-Match (CTM) planning
In this check all relevant questions and their answers for safety stock planning.
If still issue is not resolved, share one scenario with screen shots and issue faced.
Regards
Rahul