I want Sticky Notes to start when I boot up my computer, but I'm unable to find the folder where the application is.
Try searching for it in Nautilus (or Thunar if you're using lite).
Also, can you please update Zorin OS Editions in your profile to reflect what version of Zorin you're using.
In /usr/share/applications, there should be a .desktop for the application. Copy that to the startup apps folder.
You can also add applications to startup in the settings, or with a third party application, like stacer.
I would recommend making it a delayed startup (5 to 10 secs) so other libraries and dependencies are operational people to it running.
I'm using Core 16.3
Unfortunately I can't find Sticky Notes in /usr/share/applications
Apparently Sticky Notes was located here:
Now I think that you have to insert that path on a new entry on Startup Applications.