If you mean the colorful and tall garden lilies that grow on a single stalk and bloom in the summer then the best way to plant them is to purchase bulbs in the spring and plant in late spring for summer blooms. If instead you have seeds from lily flowers you already grow then this process of getting these tiny lily seeds to a bulb size takes many years and is not an easy process. I suggest you look for small bulblets close to the mother bulb that you can divide and replant and these young volunteer bulbs will bloom in 2 to 3 years. You can check my videos on You Tube to see how to divide and pot up these baby lily bulbs.  Good luck and Keep Growing, Marianne Binetti