Translations of SpotMachine is handled by The Translation Project. Download the PO file of your language from SpotMachine's TranslationProject page and edit it with your favourite PO editor, such as lokalize or poedit. When you're done, the file needs to be sent to the Translation Project robot.
Beware that your language might already have a language team, and if so, you should coordinate your efforts with them. The Translation Project has a list of translation teams, complete with contact info.