Uninstall and install for Mac

Hi. I had to uninstall Avira the free version today and when i trying to reinstall it wont allow me to. I still have the open umbrella icon in the menu bar with a red spot and when i click on that it tells me to go to my security settings and click allow, unfortunately there is not a allow button showing. I have spent the last 4 hours trying to re-install but it just wont let me. I receive the download ok but when I click open i get a message saying www.Avira is on the disk image. I click open and it all disappears. I'm climbing the walls!