Radiant default installation does not provide ways to manage the images. We can install an extension called PaperClipped, which manages assets and images with the Paperclip plugin. Here’re the more detailed steps to install it:

0. cd /home/yourradiantfolder
1. sudo apt-get install imagemagick
2. wget http://github.com/netzpirat/radiant-paperclipped-extension/tarball/master
3. mv kbingman*.tar.gz pp.tar.gz
4. cd /home/yourraidantfolder/vendor/extensions
5. tar xzf ../../pp.tar.gz .
6. mv kbinman* paperclipped
7. cd /home/yourradiantfolder
8. rake production db:migrate:extensions
9. rake production radiant:extensions:paperclipped:update
10. restart your server that runs Rails
11. login to your radiant site and you should see the Assets tab