There are 5 different plant sprinklers that can be obtained from Plant Bods.
Firstly lock the sprinklers down in your house, then you will need to fill each one.
The water sprinkler is filled by using a water tub which you can make in the tinkering menu. The water tub can be filled by targeting a water trough, you can then drop it onto the sprinkler and this will give you 100 water to use.
The potion sprinklers (greater cure, greater poison, greater heal or greater strength) can be filled with either potion bottles or kegs then again simply drop onto the sprinkler to fill.
By double-clicking each sprinkler you can tend to all of the plants in your house in one go. You will see a message in your journal which tells you how many plants have been treated.
If you own multiple houses joined together they will only work in the house the sprinklers are locked down in.