by Helen Foster.
Hi Josep,
Apologies for the hurdles you've encountered whilst attempting to contribute to the documentation and thanks for your persistence. I notice you've now managed to create a page http://docs.moodle.org/dev/Creating_a_Moodle_specific_TinyMCE_plugin and you should now be able to upload images using the upload file link in the toolbox.
For anyone else reading this thread, please note that a separate Moodle Docs account is not necessary - you can log in to all Moodle Docs wikis using your moodle.org username and password.