Hello Marie! Thank you for your email 
In order to access a task, please follow the tutorials that our team have designed: How to open a translation or revision task in the Phrase TMS Web Editor
The log in details are the same as the one you use to access the TWB Platform.
I would suggest to also read the different sections on how to work with Phrase here: TWB's Guide to Phrase TMS
Let me know if you have further questions
All the best,