Eclipse has a plugin called "Subclipse" and another called "Subversive". They can find and install those to work with their Subversion working copy directly in Eclipse. Netbeans likely has something similar.
Or, once they have a working copy checked out by TortoiseSVN, they can just import it without any special plugins into their IDE. They would use the IDE for development, and use TortoiseSVN to manage all the Subversion aspects outside of the IDE.
You won't see any changes "instantaneously". For you to see their changes, they will first need to "commit" their changes, and then you will need to "update" to see their changes.
Since you're asking a really basic question about using Subversion, I'd suggest reading or at least skimming through important sections in the SVN book: http://svnbook.red-bean.com/