How are powdered emulsifiers (such as monoglycerides) prepared for use in cooking and baking?
Emulsifiers are a type of surfactant that helps combine oil and water. They are polar molecules with a hydrophobic side and a hydrophilic side (one side attracts fat and one side attracts water). They can be used in many, many ways, so it's difficult to answer this question fully, but I can give you a few examples. 

First, I make almond milk all the time. It separates rather quickly, so I generally just shake it up right before use. But I sometimes put soy lecithin in it and put it in my Vitamix, heating it up (which helps with the emulsification) and blending in the emulsifier. This keeps the almond milk from separating in my fridge. The more I use the less separation I find. 

You can use sodium stearoyl lactylate in breadmaking, mixing it with the flour before adding the other ingredients (whisk it together). This will give you a softer crumb, more volume, and a longer shelf life.

There are many ways to use common emulsifiers as well, such as egg yolks and mustard in mayonnaise. You can also use a little mustard in a vinaigrette, or egg yolks in a hollandaise sauce.

If you are making any food which is an emulsion (such as a forcemeat) and you're finding separation of the fat/water, try using an emulsifier.