I have recently installed R 3.5.0. and have downloaded RStudio 1.1.453. I went through the installation process and I have it in my downloads. However, the icon is not the same and there is a blue and yellow shield over it. Whenever I click on it the installation process just starts again. I have deleted it and begun again multiple times. No idea what to do next!
Information about your system is often useful in helping with these sorts of issues.
If you are working with windows, that blue and yellow shield may indicate you don't have admin permissions.