You might want to post some pics to start with...

And I'm not following your teacher: there is no wall template in Revit. Walls are system families and they have no templates.

I suspect he probably meant make it out or regular walls. Thats what i did when i had a condition like that.

Hey guys, thank you for your input. I've attached the parapet I came up with...I got it to sorta work, but I'd appreciate any input you guys have. I couldn't figure out how to make the length adjustable, so I just put in the total length of the bridge. The rest of the cross sectional geometry can stay locked in and doesn't need to be changed or adjusted. Thank you for your time.

Weird, your length is adjustable... you put in a parameter for it.
Anyway, I did put in some refplanes and constraints to make the parapet's height adjustable.

btw: there are better ways to create this.

1. Create the cross-section as a Profile family. Load into your project (it's going to say "cannot create this kind of family in this view" or something. Ignore that obvious statement. Now depending on how you modelled the bridge deck you can create a sweep along the sides. If you made the deck as a Floor, go to 3D, and start the Floor Slab command (it's under the fly-out menu of Floor). Duplicate the type and rename it Parapet. Edit and select the parapet profile. Now select the proper floor edge and you're done. Select the sweep in 3D and you can adjust it's length by stretching the blue dots. You can align to model lines drawn on the bridge deck for accurate placement.
2. You could do this as a wall. Draw a wall with a width same as the base width of the parapet. You'll now need a profile which cuts away all concrete that you don't want to see. Create a new Profile family, named Parapet Cutout. Draw the parapet profile but now as a cutout. Load into project and apply to the wall. OR, select the wall, click Edit > Edit Structure. Set the preview to Section and add the reveal to the wall type.