If you were too young to register when you left the UK, you can still register as an overseas voter so long as your parent or guardian was registered to vote in the UK and you left the UK within the last 15 years.

How can I vote?

Once you’re registered, you’ll need to decide how you want to vote depending on your personal circumstances. Please note: in order to apply for an overseas postal or proxy vote you must first register to vote as an overseas voter.

Register to Vote by clicking here

Register by 20 April as an 'Overseas voter' to be eligible to vote in the UK general election on 6 May."

Source: British Embassy Budapest