Question

Where do you get the tm flamethrower in white?

Answer 1

You get it at Abundant Shrine.
>West of the house near the entrance -Bulbapedia

Comments

Ummm whats the abundant shrine.

Answer 2

TM Flamethrower can only be found in BW after the main story of the game is beaten. It can be found in the Abundant Shrine, which is found when surfing up the river that is north of route 14. The Abundant Shrine is also where landorus can be found.

Answer 3

The Flamethrower TM is only available in the post-game in B/W so you'll need to first beat the E4. Then head to the Abundant Shrine (off Route 114, just go west from Undella Town to reach it) and you'll find Flamethrower on the ground at a dead end near a pond in front of a house.

Visuals are more useful than text for this question since the TM is not in an obvious location.

This tutorial has screenshots that guide you the whole way: https://guidestrats.com/pokemon-bw-tm35-flamethrower/