You have to use form AN (Application for Naturalisation). Here's the link http://www.ukba.homeoffice.gov.uk/si...ty/form_an.pdf (FORM) and the guidance http://www.ukba.homeoffice.gov.uk/si...y/guide_an.pdf
Requirements for naturalisation if you are married to or the civil partner of a British citizen
Naturalisation
This page provides details of the requirements you need to meet for us to naturalise you as a British citizen. The information on this page is only relevant if you are married to or the civil partner of a British citizen; you should read the page on standard requirements for naturalisation if this does not apply to you.
You should read the information on this page before you make an application for naturalisation. You will need to pay a fee when you make your application. If you make an application for naturalisation and it is unsuccessful because you are not eligible for naturalisation, we will not refund your fee.
If you meet the requirements for naturalisation you should go to the applying for naturalisation as a British citizen section for details on how to apply.
There are seven requirements you need to meet before you apply:
- you are aged 18 or over; and
- you are of sound mind; and
- you can communicate in English, Welsh or Scottish Gaelic to an acceptable degree; and
- you have sufficient knowledge of life in the United Kingdom; and
- you are of good character; and
- you are the husband, wife or civil partner of a British citizen; and
- you meet the residential requirements; or
- your husband, wife or civil partner is in Crown or designated service outside the United Kingdom.
Hope it will help you. God bless.