I have a Humminbird 9 DI/GPS. Is there anyway to input GPS coordinates to show you a trail to a certain location?

Of course.

The easiest way is to have a map displayed and put the map curser at a location and push the MARK button. Put the map curser at another location, MARK, and repeat.

The best way is to record a Track by traveling that path, then SAVE it.
You start by Delete Current Track and then Save Current Track at the end.

Another way is to create a PATH on Google Earth and convert that to a Track.
You can also create waypoints on Google Earth and convert those to Humminbird waypoints to load to the unit.

I don't know if I don't understand your post but I appreciate it. Tell me this. I have a two coordinates, latitude and longitude. Where would I input that? If that is possible, would it show me a trail?

A combo long/lat is a waypoint (single location). If you entered that data you will have a waypoint displayed on the Chart View. It would not be a Trail or Track.

A Track is a line that is created on the Chart View as you move. It consists of Track Points. Trail is what Lowrance calls a Track.

This is Google Earth image of a Track from the ramp to another location on the lake. The Track was saved by me with a Humminbird unit and just viewed with Google Earth. It is a result of what I described in the second paragraph above.

The Google Earth Path function I mentioned in the last paragraph is shown here. I used the Google Earth satellite image, drew a Path that followed the shoreline to have that outline as a reference for all my waypoints on a lake that has no map of any kind. That Path was converted to a Humminbird Track.
The orange background is land on a Navionics map card.

I am floating around the lake. I want to get to that fish attractor shown on TPWD's website. I have no idea where it is actually is on the lake but I have the coordinates. I just looked briefly at the CD that came with my unit. I do not see anything that discuses this. Humor me. I don't really care what it is called; track, trail, whatever. How do I use the GPS to get me to those coordinates? Thank you!

BTW; are you viewing Google Earth on your Bird???

To enter the lat/long numbers you have to create a waypoint,
Go to the Helix main menu and then to the Nav menu tab.
Then go down to Waypoints, Routes, Tracks and right arrow the 4-way button.
Then up arrow to the Options line and right arrow.
Choose NEW and right arrow.
Down to New Waypoint and right arrow.
Edit that panel.
Change the name of you want, It will be named what would it would be if you were on the water and saved a waypoint. Edit it if you want.
Change the icon if you want.
Edit the numbers and SAVE.