First time using LTSpice
Right-Click on the NMOS4 symbol once placed on the schematic and enter the width and length there. If you have additional parameters, you're better off adding your own .model card, something like this:

.model NMOStest NMOS L=&lt;length&gt; W=&lt;width&gt; Vto=&lt;Vto&gt; ...


where NMOStest is the name you'll be giving to your NMOS. You can see more details about possible parameters in the help (LTspice &gt; Circuit Elements &gt; M). It's quite spartan, but it does help. As for the rest of the calculations, I think that's up to you.