Using the terminal to delete applications

Hi there - this is an edit of a previous topic with a few changes to try to make the question I ask slightly broader.

I have installed celtx (a free screen-writing programme) using the instructions that I found at this sight:

http://harveynick.wordpress.com/2008/08/24/mdl-celtx-on-the-acer-aspire-one/

I used the advance mode to download the application then followed the instructions from there.

I didn't get as far as finding a logo as half way through I realised that the programme didn't appear on the advanced mode menu so I stopped. This (I think) is due to celtx now being in a file call 'opt' although I'm unsure as to what that means. I am at the point now where I can run celtx using Alt, F2 and typing 'celtx' but this seems fiddly and I'd prefer to use the menu so I'm thinking about re-installing the application.

What I'd like to know is:
1.Can I remove an application using a terminal command? (in the case of celtx I can't use the add/remove as the programme is in 'opt' so does not appear in the menu). What command should I use? Should I even be messing about like this even though I'm a complete novice? I'm generally interested in this as I'm planning to install a number of applictions (such as audacity and skype - I've already installed VLC with a desktop icon using the excellent instructions on this forum) and would feel a hell of a lot better knowing that I'll be able to get rid of them and start over if things don't go the way I want it to.

Any help or links would be much appreciated and apologies in advanced if I've missed something that's staring me in the face.