How can I make my coleus spread wide instead of up?

Pinch back the small leaves in the tge middle of each stem

Pitch out the top leaves, that will encourage it to spread.

Cut the stems back about one third of the way down just above a set of leaves. Doing this causes the stem to grow two new ones. One on each side of the stem. If you look carefully you will see little leaves growing out of the stems where the leaf touches, these are what will grow. I don't cut below where I don't see these baby stems. Always cut at least 1/2" above the leaves because the stem will naturally die back some, actually it is just drying. As these grow taller you can pinch back again (just on the new stems)

Coleus are considered an annual in most areas so keep the flower brackets pinched off. If you let them grow then the plant will naturally die because its purpose is to grow, bloom and go to seed, reproduce and then die. This is true of all annuals - deadheading on other annuals will cause the plant, most of the time, give you a new set of blossoms. But with coleus you don't want them to bloom. They will lose color if they bloom and too much direct sunlight. I live in So. Cal where the sun is always very bright and they are best in the shade. Have fun experimenting and learning. These are beautiful plants.

I'd also like to say that if you put the cuttings in a glass of water they will for the most part root and you will have more plants to pot up. Just cut them, pinch off the bottom leaves (the ones that will be in the water because they will cause the cutting to rot)and let the raw parts dry up for and hour or two then into the glass of water. This too is an experiment. It doesn't work every time but if you want more of the same or maybe a friend or another gardener has a different one than yours this is the best way to get new free plants. I pot mine up in a small pot when the roots are about 1/8" maybe a little more. If you leave them in the water too long they usually rot.

Pinch off the tops of the coleus and it will branch out and get bushy

http://www.finegardening.com/video-pinching-coleus

Pinch out the flowering piece that grows in the middle of the leaves