Take this with a grain of salt because I haven’t gone through this process myself.
I can’t make any good recommendations for cheap certificates as most currently offered at low prices are somehow associated with Comodo (they have been breached not too long ago, thus the price reductions).
The Answer Nick Tempe gives works perfectly if you are self signing the app.
If you do end up purchasing Code Signing Certification (if you need to have one for clients or to avoid the Windows prompt of it being software from the internet that may not be safe) then you will want to add some aditional flags to the signtool command.
My company needed a EV Code Certificate and the command that we use is:
signtool sign /fd sha256 /tr http://ts.ssl.com /a
If you will have an installer for your app be sure to sign the installer as well. If you use Inno to create your installer you can set it up to run the signtool automatically when the installer has compiled more info about that here: Inno Sign Tool
Being a single solo developer, all you require is Individual Code Signing Certificate which is highly suitable for solo developer code security requirements and software validation purposes to users.
You can get an affordable Comodo or Sectigo Individual Code Signing Certificate from any trusted reseller rather than CA like I usually obtain an Individual Signing Certificate from SignMyCode at a very affordable pricing of just $210.99/year!