Learn Finnish: Me veimme mustan kattilan ulos. - We took the black pot outside.

Viedä is a Type 2 verb. Its stem is vie-, which ends in the diphthong ie (two vowels together). To form the past tense, the rule is to drop the first vowel of that diphthong (the i) and replace it with the past tense marker -i-. So vie- becomes ve- + i- = vei-. Then, just add the personal ending for we, which is -mme, resulting in veimme.

Why do musta and kattila both have an -n at the end?

They form the object of the sentence. Because taking the pot is a completed action involving one whole object, it takes the genitive-like accusative case, which ends in -n. In Finnish, adjectives must match the noun they describe, so both musta (black) and kattila (pot) get the -n ending, becoming mustan kattilan.

I thought the word for outside was ulkona. Why does this sentence use ulos?

Finnish uses different words for location versus direction. You use ulkona when something is already located outside (like The pot is outside). You use ulos when there is movement to the outside (like We took the pot outside). Because the verb viedä involves movement to a destination, we must use the directional word ulos.