putting a tube in a spice schematic

Go to misc to fine the symbol.

Select triode

Put the triode on the screen and select "spice directive"

Type in .inc and click ok.

This places .inc on the screen. Click it.

Click browse.

Locate your model and click it.

You now have the model and symbol on the screen.

Ground the cathode because spice does not like floating circuits. Hit run and enter a stop time. I usually use 10m.

If you installation has this directory you uae a different procedure to find the model bear with me on that.

The Valve directory offers a triode symbol too.

Look back and you will see TRIODE was displayed when the symbol was placed on the screen. Click triode and a box will open. If it has an arrow you can pull down a menu and select a tube otherwise you type your tube in. In this case 12ax7.
now the sim should run. In a basic LTSpice IV install you will not have as many options. We have tube libraries available from 4 sources (maybe more) so we have to match our symbol to our model. Some models include the filament which complicates matters further. Once you load and run your first sim just make a note which symbol you used. The models I sent out are "generic" meaning work with the spice model which came in the bundle. I hope this helps.