Hello All,
I had pasted some files on my desktop. These files opened with a preset default application. I wanted to use another one that I installed but on right-clicking the file, no option for opening in an alternate application was available. Even googling for help did not yield any usefull results. Finally while checking out some files in my home directory ( using the default Thunar browser) I found that inside Thunar the alternate application option is available and I could change it to my chosen one.
Plus, those who do not have the archiving option on right click inside Thunar can install the 'thunar-archive-plugin' using apt-get. This will add the archiving options 'Extract Here' and 'Extract To' on right clicking files inside Thunar.