If you prefer to translate offline using a desktop tool, you can download the content from Transifex, then import the finished translations back into the project.
To get a file for translation:
From the project navigation, select the project that has the file you want to translate.
In the list of resources, select the one you'd like to work on.
Click on the language you want to work on.
In the popup, click either Download file to translate or Download for translation as XLIFF. A file will be saved to your computer.
If you chose the "Download file to translate" option, the file you get will be in the same file format as the source file in the project.
When you're done translating the file, you can import the translations to Transifex.