There is a General Election on 12th December; in order to vote you will need to be on the electoral register, a list held by Lewisham Council.
To get on that list, you need to use the Government’s Register to Vote website. This works using a smart phone and/or a desktop computer or laptop. The latter can be found in most public libraries.
Make sure you’re registered to vote by midnight November 26th.
The Council’s instructions on how to register are on this page.