
If you are a Custom Button creator, you have just to :
1. Create a new topic in this subforum with a title of this format
[BUTTON] Button Name
2. Either attach a simple .txt file (please stick to utf-8) on the top post with your strings to translate or simply copy-paste the string list on the top post.
If you are a translator, you can also attach a .txt file with your work to your answer with an explicit name
such as fr-FR_MyButton.txt
An example of topic creation an answer is available here