If your account is configured for this, there is some subtitle support available in Console. On the "Edit" page of videos, you should see a box for managing subtitles near the bottom of the page:
To upload a subtitles file, select the language for the subtitle, click on "Browse" and select the subtitles file, and then click upload.
N.B: Only one subtitles file should be uploaded for a given language at a time. Uploading subtitles for a language where subtitles already exist may result in only the latest subtitles being shown, depending on which player your account is configured to use.
To delete subtitles, click the bin icon next to the subtitle in the list.
The icon between the bin icon and the subtitles language indicates the processing status of the uploaded subtitles (i.e. Successfully processed, Failed while processing, or Processing in progress):