How do I prepare for the MLAT?

The MLAT is a very wide-ranging test that covers all modern languages taught at the university, and also linguistics. If you are preparing for a language you have studied to A-Level, then you need to have a firm grip on grammar, and you can do that by using textbooks, practising past papers (see link below), using online tools and using testing apps. If you are doing a language from scratch, or if you are applying for linguistics, then you will answer questions to test your language aptitude, and to do that you can practice using past papers from here: https://weblearn.ox.ac.uk/portal/site/:humdiv:modlang:mlat-tests, or you can use the sample questions from the international linguistics Olympiad.