Leaks

I have a leak. The pool pump has not beenrunning and the water has leaked down about 4 inches below the pool light. The skimmer still has water in it. I suspect that the leak is somewhere between the bottom drain/return and the pump. Somewhere in the line. I bout the 32 oz Fix-A-Leak. Any suggestions on how to use the product with this situation? My thinking is that the product needs to be poured directly into the bottom drain and recirculated back to the bottom drain using an alternate PVC pipe from the pump back to the drain. Any suggestions?