During early September, you will be invited to register your Skills via the on-line Demonstrator Skills Collection form:
All PhD students should do this, whether new or current, since invariably there are changes each year to the various skills required.
Do this every year when you are informed via email that the System is live (usually in August or September) or as soon as possible after you arrive back in the School (returning postgraduates), or join the School for the first time (new postgraduates). It is most important to complete the form every year -- if you do not do this then you will not be allocated any demonstrating.