The hose coming from my air filter box to my engine is loose. There's nothing to secure the hose to the box. My guess is that it had a grommet at one point. Any suggestions on how to hold it in there? I'm not sure where to get another grommet. It's an inline six btw. Also the hose in the picture is not my truck. I found of an image of it for better clarity.

 

I believe this is what you are looking for.

PCV Elbow 300/302/351-Broncograveyard.com

They sell on amazon as well.

While your at it I would replace the PCV valve (thing that protrudes from the top of the valve cover) as well so that the PCV system is working properly. If left unattended can lead to seal leaks, carbon deposits, etc. You can buy the motorcraft PCV valve on amazon or ebay for less then $10. I used an offbrand one (autozone branded) and the ball in the valve is so noisy I ended up ordering a motorcraft one but have yet to install.

 

There is a filter inside the air box that the hose attaches to called a "breather element". This is to filter the air going into the engine via the breather tube (the subject of your post). The breather element is held in place by a clip, which also has 2 fingers that grab the elbow listed by fordf350man, to hold it in place. It looks like this:

Dorman 41112 Air Filter Accessory Gasket Breather Element Clip | eBay