:term:`Editor links <Editor link>` form a connection between the Numbas LTI tool provider and an instance of the Numbas editor, allowing instructors to select exams from a list inside the LTI tool, rather than downloading an exam package to their own computer and then uploading it to the LTI tool.
The public Numbas editor hosted by mathcentre provides a wealth of ready-made exams on a variety of subjects.
From the :ref:`admin interface <admin>`, click on the :guilabel:`Editor links` button at the top of the screen.
Click on the :guilabel:`Connect to a Numbas editor` button. In the :guilabel:`Base URL of the editor` field, enter the address of the Numbas editor.
The address of the public editor hosted by mathcentre is:
https://numbas.mathcentre.ac.uk
Once you've created an editor link, you can select the :ref:`projects <numbas:projects>` from the editor that you want to use.
Only projects which are :ref:`marked visible to non-members <numbas:public-project>` are available. This is because the editor link has no authentication mechanism, and linked projects are available to all :ref:`consumers <consumer>`.
Once you have selected some projects, published exams from those projects will be available for instructors to pick on the :ref:`new Numbas activity <create-resource>` screen.