Basically the water overflows into the sump (you mentioned the tank is drilled, so I will ignore overflow boxes) through the drilled holes. Obviously you need hoses connected, usually using bulkheads to get a waterproof seal on the tank.
The hoses feed the water into the sump over the blue "bio balls." With the model you have there should be a tray that a filter pad sits on (the tray is drilled with lots of small holes to drip the water over the bio balls). The water then flows through the balls and into the other side where you should have a pump that forces the water back into the tank.
The pump sits on the "empty" side of the sump and as this side fills with water the pump constantly pumps the water back through another hose where it returns to the tank (there are a few different ways to do this, so I just described what is probably the most likely way the previous owner did this and easiest way to do it).
Two things to really look out for is to make sure you don't allow your pump to run dry (will burn out the motor), just make sure you top off the water as necessary. The other thing is there should be some failsafe in case the power shuts off or your pump dies. Basically you want to make sure you don't continue to have water overflowing into your sump so that it overflows because water isn't being pumped back to the tank - I think this is bigger problem with overflow boxes (which I don't think you have), but something to look into so you don't end up with water everywhere.
The hoses feed the water into the sump over the blue "bio balls." With the model you have there should be a tray that a filter pad sits on (the tray is drilled with lots of small holes to drip the water over the bio balls). The water then flows through the balls and into the other side where you should have a pump that forces the water back into the tank.
The pump sits on the "empty" side of the sump and as this side fills with water the pump constantly pumps the water back through another hose where it returns to the tank (there are a few different ways to do this, so I just described what is probably the most likely way the previous owner did this and easiest way to do it).
Two things to really look out for is to make sure you don't allow your pump to run dry (will burn out the motor), just make sure you top off the water as necessary. The other thing is there should be some failsafe in case the power shuts off or your pump dies. Basically you want to make sure you don't continue to have water overflowing into your sump so that it overflows because water isn't being pumped back to the tank - I think this is bigger problem with overflow boxes (which I don't think you have), but something to look into so you don't end up with water everywhere.
