A phot would help. What is wrong with it?
What's it made if? Usually if cracked best to replace. Will leak and cause floor to rot.
If it's fiberglass, this link should help:
If its a small defect you can repair with JB Weld..... https://www.youtube.com/watch?v=ttslk2ijN6Y and then you can also use 2 part epoxy tub and sink repair kits to paint the repair. https://www.youtube.com/watch?v=ttslk2ijN6Y