Sounds right to me. You can use the holes that are already in it - your choice what you want to do with them.
You'll basically need overflows that will get the water to the sump, the water goes through the sump, and then you use a pump to pump that water back into tank. A pump is constantly pumping water from your sump to your tank, the tank overflows and drains into the sump.
Use the holes for your overflows and returns. When i did mine, I used the bigger holes for my overflows and the smaller holes for the returns.
You'll basically need overflows that will get the water to the sump, the water goes through the sump, and then you use a pump to pump that water back into tank. A pump is constantly pumping water from your sump to your tank, the tank overflows and drains into the sump.
Use the holes for your overflows and returns. When i did mine, I used the bigger holes for my overflows and the smaller holes for the returns.