Before starting to translate a footage please be sure that you choose a footage that is not assigned to another translator, those assigned to "your name" are free to edit. Then just edit this page and replace "your name" by your real name on the footage you choose and save, then people know you are working on it. After this click on the "Edit subtitles" link corresponding to the footage you choose. You will be redirected to an online subtitle editor, where you can start to translate. Before this we suggest you to take a look at the editor documentation to figure out how it works. Once you translation is completed just export it in "subrip" format from the editor, and copy/paste the result it the "Save subtitles here" link corresponding to the footage you translated, and save :-) Finally re-edit this page a replace the footage status from "pending" to "done".
Please take time as well to talk and introduce yourself in the translation forum for welcoming and manage efficiently all efforts.
Thank you!