First of all, you need to loosen the soil where you want to plant the pole beans. You should also remove all weeds from the planting area and mix up compost, peat moss and manure in order to make the soil perfectly suitable for growing pole beans.
Mixing up compost, peat moss and manure will help in fixing the drainage fertility issues of the planting area and the pole beans will grow in a better way.
You should take a 2 by 4 sized board and drive it in the ground about at least two feet deep. Use a hammer for that purpose. Now take another board and do the same process but it should be almost 7 feet down the row.
You can alter the height of the trellis as desired by cutting both of these boards. However, make sure you make the boards shortened to such a size that is completely fit for the trellis.
Now take another 2 by 2 board and nail it across the top ends of these two boards. Now, you should nail another board which should be six inches above from the surface. It will provide a solid support to your trellis and without this support the trellis will not stay stable.
Then take a wire and wrap it around the bottom of trellis support for at least twice. Now, you should use a pair of pliers to twist the wire around the top board twice which will secure the ends. Now you should put a wire besides the horizontal supporting boars with a distance of almost 6 inches.
Now plant the seeds of beans at least one inch deep in the soil under each wire. Make sure you plant one seed under one wire and when you see the seeds have started sprouting out for at least 6 inches then give direction to the plant by gently wrapping it around the trellis wires.