The long pause is partly because you didn't really give enough information for anyone to use. And partly because using a dehydrator is rather dependent upon experimentation. You get the material ready and then you keep checking as the material dries, and eventually you learn what to do.

Basically, a dehydrator removes excess water from the material. How long it takes depends on the original "wetness" of the item, how thick it is, how much humidity is in the air blowing over the item, and whether or not the air is heated. A thin item in warm air in an area of low humidity will dry much faster than the same item if it is thick and the air is moist.

By herbs, I will guess that you are referring to the leaves of various plants. In general, you pick the leaves at the peak of freshness (early morning), and rinse to remove any dust. If you have a salad-spinner, that is a good way to remove the rinse-water, otherwise you need to pat the leaves dry with a clean towel and then spread the leaves in a very thin layer on the dehydrator's mesh rack. If the dehydrator has a fan, you may wish to cover very small leaves with a paper towel or some cheesecloth to prevent them from blowing. Herbs usually retain the best flavor with a very slow drying, and keep them in the dark. Since the time can vary so much, you will need to check them on a regular basis. Stir and the pinch to see if the leaf crumbles -- if it does, it is dry. I prefer to stir each time I check the leaves... at the very end, you need to be sure there are no "slightly" damp areas which could spoil the batch. Store in an airtight jar in a dark place. I'm one of those who think the flavor is retained better if the jar is stored in the freezer, but that isn't really a requirement. Seeds are basically treated the same way although you don't have to rinse them after removing the husk or seed-cover.

In my area, in the summer when it is usually humid, in my rather large dehydrator: drying marjoram leaves usually takes 4 to 6 hours; sage takes longer (the leaves are larger and have more water to start with), sometimes as much as 12 hours. Apples in 1/4" slices take about 18 hours and fruit leathers take from 4 to 24 hours--- it really does depend on the moisture and how thick the jammy-stuff is. I don't use the heater portion of the unit for those items... if I did, it would probably cut the time in about half, but personally, I don't care for the taste that quick-drying sometimes imparts.

I strongly suggest googling to get more information about drying foods. Also, it is very possible that the manufacturer has a website with detailed information, or at the least, a number to call for help.

I know you want to use your dehydrator, but you might like to try drying small amounts in the microwave. Spread on paper towels and nuke for a few minutes, checking every minute. Soon they will be dry and crumbly. They stay nice and green and do not lose fragrance.

I have dried some of my herbs by placing one layer only of herbs on a cookie sheet lined with a paper towel and placed them in a frostless refrigerator. Depending on the herbs, it can take a week or two to dry, but I have had good results this way.