hit the V button on your keyboard to bring up your actions. Click on the general tab and scroll down until you find the cultivate icon (mushroom). Click and drag it to your hotbar.
This will bring up a window with 4 boxes in it representing plots, you will only have one plot available (no clue how to get any of the others up). Click and drag the items you want to use from your inventory (bank won't work has to be inventory).
That's all there is to it.
Sorry for this taking so long. When you hit 50/100/150 skill level, another plot opens up. Bouncing between 2 is already fun, 4 might be too crazy.
BTW, in the guides section, there are three headings for cultivators, alchemists, and talisman makers. If you can copy the basic from out of each of those for the recipes, then take the time to enter in your own recipes and the results, it would be really fantastic. Hopefully we can build up a large database of known recipes and make everyone's life easier.