How do i export a model to the source engine?

Is there a tutorial out there teaching how to export a model to the source engine? I am making a massive multipurpose gmod map, and i am mapping it in episode 2 sdk, i made a fantasy factory, and just finished the model for the dyrdek enterprises inc. sign. How do i save it in the right format so it can be used in gmod and the episode 2 hammer editor? It doesn’t use any textures i just colored it blue.
edit: also how do i know if it is the right size? I think it might be too big or even to small.

wait, are you trying to put a model into source? If so, what program are you using, and what format do you currently have your file in?

I am using SOFTIMAGE XSI, i don’t know what format it’s in but I haven’t saved it as anything, it’s just a project. And yeah, i’m trying to put it into source, or whatever format so i can place it in the episode 2 engine and gmod, just as a prop, no animations or anything.

at the top of the window(same line as file, edit etc), it should say valvesource. Click on valvesource and then click on .smd exporter, and the rest should explain itself.

Have u installed the Valve Source addon?