To use NEStra, press "Alt+F2" and type in "nestra". Alternatively, go to terminal and type in:
For the other emulators, go to terminal and do the following (you may want to look at the file called "INSTALL" which should be in each of their directories before doing this):
$ cd directory_of_emulator
$ make install
If you have a problem during the ./configure phase, then please post the error message.