Certified GKH Gardening Expert
The following article should help you with this: https://www.gardeningknowhow.com/edible/fruits/lemons/how-to-grow-a-lemon-tree.htm
First take the seed from a lemon and peel the outer skin off. Wash them and put them in a moist paper towel in plastic bag.After 2 weeks check them. There should be a root growing out of it. Plant it in soil and water. There, just let it grow and you will have a lemon plant. It may take years for it to produce lemons. I did this and it worked great!