If you willing to help translate Brave to Finnish, I can give you steps to get started. 
- Brave use Transifex for localization effort. You can create an account if you don’t have one.
- And go to this Finnish (fi) language project https://www.transifex.com/brave/brave-laptop/language/fi/
- Click Join team, and if your request accepted, you can start to translating!
- For translating, click resource (eg. adblock.properties) that you want to translate. And then click Translate button.
- Voila! Start translating the available strings.
- You also can provide another suggestion for already translated strings if you found a mistake or misspell.
- Once the progress reach 100% (all resources translated), PING us so the team can include Finnish as language option.
Feel free to ask if you have a questions.
Best