This will help you out: Enhanced Tracking Protection is a collection of Firefox features that protect your privacy while you browse. See Enhanced Tracking Protection in Firefox for desktop for details.

How do I get the purple shield on the address bar?

Hello WildChildShirl56 ,

Just in case you are talking about the purple mask:

You will only see it when you are in   "normal mode"   and open a   New Private Window.

When you are in permanent Private Browsing mode,   you won't see a purple mask.

You normally see a black shield at the left end of the location/address bar when you visit an HTTP or HTTPS internet web page (i.e. not for internal pages or local pages).
This shield is highlighted purple when Tracking Protection is active and blocking content and you can click the shield for more info.
Don't you see this shield icon ?

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware

Can you attach a screenshot ?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot