If you are at or above 18 and wish to apply for British Citizenship, you may do so, if

1. You have spent a continuous period of 5 years in the UK up until the date of your application
2. You have not been absent from the UK for more than 90 days in each calendar year
3. You have not been absent from the UK for more than 450 days in total
4. You have been holding Indefinite Leave to Remain for at least 12 months before the date of your application

Furthermore, there are requirements of you being a person of ‘good character’, and the Home Office reserves the right to refuse your application if they believe granting you citizenship would lead to public disorder.