How do I start a avocado plant from a seed of a avacado I purchased a

set in a small jar or glass n fill half with water. then put fat side down in water. half of avacado is all that should be covered in water

https://www.californiaavocado.com/how-tos/your-own-avocado-tree

They are tough. Got a big potted plant inside? Dig a hole ,put the seed in with point up, cover it and in a couple of weeks you will see it. Outside, do the same thing, it does not like soggy soil.....full sun works best.

To start a Avocado plant, first of all what kind did you purchase. some take quite along time. My mom and dad would use Hasa Avocado...First Step use a Clear Jar Mason fill with water enough that tip of Avocado will touch water about 1/3 will submerge in water. Second need to round toothpicks poke tiny hole almost slightly slant with toothpick leave in, cause that is what will sit on rim of jar to keep Avocado not complete let in water. Remember Tip will be sitting in water, put on window sill or where some light comes in..eventually you will see roots growing it can take along time but its worth it, you also can plant it outside to produce Avocado or as House plants

I used to do this with my students! https://www.youtube.com/watch?v=uvLKkoGxxBQ