The glass test tube should have a black dot or black line at the bottom of the tube. This mark is crucial to the testing process, so make sure that it is there. Sometimes the test tube and the plastic vessel are connected, but there should at least be two separate compartments.
Some testing kits will provide a plastic vessel that has a lid. When this is the case, you can mix the reagent into the sample water by capping the vessel and shaking it for 30 seconds or so.
