Docs needed: Running many towers at once on a node

[samsrabin]

What sort(s) of issue is this?

• [x] Something is missing.
• [ ] Something is (or might be) incorrect.
• [ ] Something is confusing.
• [ ] Something is broken.

What part(s) of the documentation does this concern?

• [ ] Technical Note (science and design of the model)
• [x] User's Guide (using the model and related tools)
• [ ] Somewhere else (e.g., README file, tool help text, or code comment): Please specify
• [ ] I don't know