You will have received am email from 'Admin at LTSC' with your login and password.
You will see a lits of available dates to swap with, select the date/role you wish to srequest a swap with. If they agree then your rota will be updated.
If you want to select a date that has no volunteer yet then volunteer for that new dates then select a duty swap for your old date and select 'LTSC Admin ~ Special @ Special Event for Rota Swaps (31 Mar)' and add in the comments that you have selected another.