Firstly you should read the advice on extending your visa here: Guidance Notes.
Secondly you need to complete a Confirmation of Acceptance for Study (CAS) Request Form.
It is very important that you prepare the supporting documents for your CAS Request Form in good time; it will not be possible to issue you with a CAS until you have provided all the correct supporting documents with your CAS Request Form.
Some students are not able to extend their visa in the UK; if you are advised that you cannot extend your visa in the UK you will not be issued with a new CAS until you have provided a scanned copy of your boarding card for your flight home to The Student Immigration and Compliance Team (SICT) SICTSupport@uclan.ac.uk.
Standard Student Route visa applications make take several weeks to be processed by the Home Office; the average time is 8 weeks, but it may take longer. You should not make any plans to travel outside the UK if you need to make a standard Student Route visa extension.
The University cannot speed up your visa application with the Home Office. If you prefer, you may wish to use one of the Home Office’s faster services – either Priority or Premium: www.gov.uk/tier-4-general-visa/extend-your-visa. Please note that both these faster services cost considerably more than the standard service. For further information on the Premium Service: www.gov.uk/ukvi-premium-service-centres/overview.
This leaflet explains what a biometric residence permit (BRP) is, what it can be used for, and how employers can check that prospective employees have a right to work in the United Kingdom.