I downloaded the program and my computer asked me how I wanted to open it. It was set to Adobe as default and now I cannot change it or open it. Is there a way to do so?
Are you using Windows and trying to open it with the file manager?
If you have followed the installation instructions you should be able to open a command prompt and type "exiftool" to get it to run.
https://www.exiftool.org/install.html
To be clear, you're saying that Windows (assuming you're on Windows) now wants to open the ZIP file you downloaded with Adobe?
If you're using Windows 7 or greater (not sure about vista), right click on the icon, select properties, and click the Change button next to "Opens With"
(https://i.imgur.com/0dlL2Et.png)
You should then get a box that asks you what program to open with. Look for "Windows Explorer" or "File Explorer" or something similar. You may have to click "show more apps" at the bottom.
(https://i.imgur.com/TrR0Pok.png)
After selecting that, Windows will treat zip files as Compressed Directories and will open them up just like a directory. Drag Exiftool out and follow the instructions greybeard linked to.