Learn Farsi: چراغ‌ها اینجا است.

By adding the regular plural suffix ها (-hâ) to the singular noun چراغ (cherâgh, meaning "light" or "lamp"). Just like adding "-s" in English, you will use ها at the end of almost any noun in Farsi to make it plural.

Why does the sentence use the singular verb است (is) instead of "are" for plural lights?

This is a very important rule in Farsi! When a plural subject is a "thing" (inanimate object) rather than a person, the verb is usually singular. Since lights are objects, Farsi literally says "The lights is here."

What makes up the word اینجا (here)?

It is made by combining این (this) and جا (place). So اینجا literally translates to "this place", which is the standard way to say "here" in Farsi.

Why is the verb است (is) at the very end of the sentence?

Farsi sentence structure usually puts the verb at the very end. The natural order here is Subject (چراغ‌ها / the lights) + Location (اینجا / here) + Verb (است / is).