If you are interested in becoming accredited or you are an accredited centre applying for renewal, all the information you need can be found here.
If you want accreditation for visa purposes for non-English language courses there is a list of recognised accreditation bodies on the Short Term Study Visa page of the gov.uk website.
In order to recruit students on Tier 4 visas you’ll need to meet the UK government’s requirements for educational oversight. Details are available on the gov.uk website.