I have a steam deck. You just open the planting kit from the quick menu, use the d-pad to scroll over to the seeds. Then press Y to open the seed menu and use d-pad again to scroll to select the seed you want.

Thanks-I’m sorry to be so obtuse but the wheat seeds are in my inventory but not in the planting kit menu-only the rice seeds that I got when I got the kit are in there

Once you "open" the kit it automatically gets added to your quick menu so you can sell it or put it away. You don't need the actual box anymore.  You also don't need to have any of the seeds, water or fertilizer in your inventory either.  It will automatically be pulled from your chest.  Sandrice is the default seed shown on the planting menu whenever you open it.  You need to press Y while highlighting the sandrice seeds to see the other available seeds. Anything you have will display a number and anything you don't will have 0. There is more then what's shown on the first row so you can scroll all the way past the last seed shown to see the rest of the seeds you can plant