Marshaine, Either hang it or put 1/3 of the tire beneath the ground. Plant it like any other plant ,some dirt and water. Aloha!
Drainage is key.
Either put gravel and sand in the bottom, or drill small drainage holes in the bottom or put individual pots in the tire & put something like sand or spagnum moss around them.
Just lay the tire down where you want it, fill with potting soil and plant. You can also stack tires if you have more than 1.
Another way is to dig a hole the width of the tire, put about 1/4 to 1/3 of it in the ground standing up, fill in the hole and plant.
You have several options Mashiane:
1. For Larger tires, You can get a 'Table Top of Wood, like you use for making Lazy Susans' from Home Depot. Ask they and they will direct you to the 'Wooden Rounds'
They have at least one that fits snugly inside the Tire.
You need to measure the Tire Inside Diameter to get the right diameter. You place that Inside, and you can fit a great portion of a Bag of Potting Soil inside.
2. If it is a Smaller Tire and you really want to make that Permanently into a Planter and Skip on the Wood, you can pour 2 inches of Cement into the base of the tire while you rest the Tire on a Flat Ground.
You can then Hoist that tire up on a Tree just like you would a Tire Swing by getting a 'Tire Swing Kit'. Put Soil in after you hoist it and then you can plant within.
Put landscape fabric in it first to hold potting soil or place a board across the hole then the fabric. Here's ALOT of ways to use them as planters & how to do it just click on one of them to see what these people have done https://www.youtube.com/results?search_query=tire+planters+ideas