There are two parts to the Knowledge of Language and Life in the UK (KoLL) requirements.
All applicants that want to apply for citizenship or settlement have to:
The Home Office now only accept Secure English Language Tests (SELT) for settlement or naturalisation. SQA ESOL certificates and any other English language test are no longer accepted.
The two SELT assessments are provided by Trinity College London and IELTS SELT Consortia in the UK.
You can sit the Trinity SELT in Glasgow. More information and how to book can be found at this link: http://www.trinitycollege.com/site/?id=3218
You can sit the IELTS SELT in Edinburgh. More information and how to book can be found at this link: http://takeielts.britishcouncil.org/ielts-ukvi/book-ielts-ukvi
More information about SELT tests can be found at this link:
UK SELT Tests
More information on applying for citizenship or settlement can be found on the UK Government website: https://www.gov.uk/browse/citizenship