Through Arkindex web interface, you will be able as a Project contributor to:
View all existing transcriptions.
Create new elements, of any existing type on the project (usually lines, words or paragraphs, ...).
Then add a transcription to these elements.
You can read all existing transcriptions of an element by selecting an element on the Children tree on the left side of the screen: all transcriptions will appear on the right side in the Transcriptions panel.