As long as they are the indeterminate type tomatoes, you don't have to do anything really. They will keep growing and expanding. There are different schools of thought on whether or not to pinch off the early tomato blossoms. I never pinch them. Sometimes the early blossoms drop off by themselves but I just let the plant do whatever it is going to do at that state.

If you pinch off the growth tip at the top of the plant on the other hand, that will stunt the growth of the plant. You definitely don't want to do that now. Some people prune off the grow tip of the plant at the end of the season so the plant will stop growing and put energy into ripening the last fruit of the season. I never tried that technique.