If you are qualified to vote in the upcoming referendums but your name is not on the register, you can apply to be included in a Supplement to the Register on form RFA2. This will allow you to vote at any election or referendum held during the year. You can apply for inclusion on the supplement as a result of changing address on form RFA3. This will also remove you from the register for your previous address.
You must apply for inclusion on the Supplemental Register at least 15 days before polling day (Sundays, are not counted as days for this purpose) so today, Tuesday 5 May 2015 is the last day for the referendums that take place on Friday 22 May 2015.