Here's the easiest way to get a little grain onto your image. In the Viewer, click on the button on the bottom right with the little "A" on it. Select Render, then Noise. In the Viewer you'll see what looks like TV static. Put this on a video track above the video you want to give the grain effect to. Lower the opacity to about 3 or 4 and you'll get a nice film grain effect.
To get the video to look more like film, take your original video clip, make a copy of it and place it on a video track directly above it. Lower the opacity to 50%. Deinterlace the top clip upper field first and deinterlace the bottom clip lower field first. Add a gaussian blur filter to both clips at about .7 to soften the hard video edges. Apply the film grain technique from above and the results look pretty good.
Film look plugins like Nattress and Cinelook and Magic Bullet do a very good job, but if they're beyond your current budget this free technique will get you by.