If the tank does not have quick disconnect connection you have to cut the lines.
There should be screws holding the tank to the back wall.
For some reason the water tank is not shown on your model but here is a part number for a new water tank. This is the PartSelect part number PS291933.
You may want to check with Hotpoint to make sure that this is the right one. The original part number is WR17X10734.
Here is a link to your fridge model HSS25GFPHWW. | 
Water tank problem 
