How to patch / add a plugin to Joomla CiviCRM?

We have the CiviCRM Admin Bar showing up on the Front-End of our site and I've found a possible solution/patch, 'https://github.com/civicrm/civicrm-core/pull/13820, but I don't know how to install the patch. I've downloaded the .zip of the patch from github. Now what do I need to do to get it installed on our site? Thanks in advance for any assistance you can provide.

Aidan's answer is a good one in your case! However, the general process is this:

• Find the URL of the patch. As you note, in this case it's https://github.com/civicrm/civicrm-core/pull/13820.
• Add .diff on the end, e.g. https://github.com/civicrm/civicrm-core/pull/13820.diff.
• Save the file to your computer and upload it to the server in the civicrm directory. Let's assume it's called 13820.diff.
• Run this command: patch -p1 < 13820.diff. Note that if the patch doesn't apply cleanly - for instance, the file has undergone changes - you'll get a warning. Otherwise, it will be successful.

If you can edit files on the server but don't have command-line access

• Find the URL of the patch. As you note, in this case it's https://github.com/civicrm/civicrm-core/pull/13820.
• Click on the "Files Changed" tab.
• Note how many files have changed (see screenshot). In this case, it's just one.
• Note the name of the file that's changed (see screenshot). In this case, it's CRM/Core/Resources.php.
• Make a backup of the file that you're going to change!
• Remove the lines in red on the left side, replacing them with the lines in green on the right side. Use the line numbers to make sure you're changing the right lines!
• Save the file.
• Thank you. Since we are already running 5.12.0 and the patch I was seeking to add is include, I don't need this now, but I'll save it for later use. – Fred Apr 13 '19 at 3:38

What version are you on now? That patch is in 5.12.0 so your easiest option may be to upgrade to that version.

• Thank you. We are running 5.12.0, but the problem still exists. We have the Admin Menu Bar showing up when the Event Info page is displayed. – Fred Apr 13 '19 at 3:37