If we are talking SDLTRS (the one linked from the emulator wiki page) then there is an official webpage here:
http://sdltrs.sourceforge.net/ which contains amongst other things a user guide and stuff like that. We've spoken earlier about this page here:
http://www.classic-c...em-80/index.htm which is properly for the System-80 (a TRS-clone) but it contains "driving instructions" for using a TRS machine.
I've tried starting the emulator, and it seems you need to have a dump of the system roms. I do not know of the proper legal status for those, but they can be quite easily found by looking around a bit. The system roms, here, are not games or anything like that, it is rather the contents of the computer roms itself - that is. the basic interpreter and so on.
Anyways. You get to the main menu of the emulator by pressing F7 (F8 quits). From there, you can do the usual stuff - attach disk, tape and hard disk images, select system roms, configure which type of TRS you want to emulate, and so on. From what I can see, the file selector stuff (selecting disk files or system roms or such things) wont go out outside the /mnt directory, so you need to put .dsk and rom files in the appdata directory. Just run the emu once to create the directory, and then you can put the files in it.
So far so good. I'll go get some roms and see if I can get it started.