The way you choose to register will depend on your personal circumstances.
You can register as a service voter using this form or by registering to vote online.
This allows you to be registered for five years at a fixed address in the UK even if you move around. You must renew your application every five years, but you can cancel it at any time. Registering as a service voter is particularly useful if you are based overseas or think you may be posted overseas in the next few years.
Your unit has a designated Unit Registration Officer who will be able to give you more information and advice. Ask your administration office for contact details.