Learn Finnish: Nauttikaa tästä retkestä!

To make the plural or formal command for Verb Type 1, you take the dictionary form (nauttia), remove the final -a, and add the ending -kaa. Notice that it keeps the strong double consonants (-tt-) from the dictionary form, unlike the "I" form which weakens to a single -t- (nautin).

Why do we use the -stä ending on both tästä and retkestä?

The verb nauttia (to enjoy) always requires the thing you are enjoying to be in the elative case, which means adding -sta or -stä. While in English we just say "enjoy this trip", Finnish logic thinks of it as enjoying "out of" this trip. Since retki gets the -stä ending, the word for "this" (tämä) must match it, becoming tästä.

Why does the verb end in -kaa with an a, but the other words end in -stä with an ä?

This is due to vowel harmony. The verb nauttia contains the back vowels a and u, so any suffixes attached to it must use back vowels like a, giving us -kaa. The words tämä and retki only have front vowels (ä, e, i), so their endings must use the front vowel ä.

Can I use nauttikaa if I am only talking to one person?