Explain the procedure to apply …

To apply for UK citizenship through the naturalisation route, the individual must meet certain requirements set by the UK government. These include being 18 years of age or older, having indefinite leave to remain (ILR) or permanent residence status, be of good character, pass the "Life in the UK" test and satisfy the knowledge of language and life in the UK requirements.

Source

1. Check your eligibility here. If you meet the eligibility requirements you can proceed to the next step.
2. Complete Form AN (Application for Naturalisation as a British Citizen) and gather all other required documents.
3. Pay the application fee.
4. Submit your application form and documents to the appropriate Home Office.
5. Complete the "Life in the UK" test and obtain your pass certificate.
6. Attend an interview where Home Office officials will assess your application.
7. You will receive a letter informing you of the decision on your application. If successful, you may need to attend a Citizenship Ceremony.
8. You will be sent your certificate of British citizenship and a registration certificate when you have successfully completed all stages in the process.