You’ll need to register for the LNAT and book a test slot at a local test centre. The deadline to do this for the majority of universities is 15 January 2018, or 5 October 2017 for the University of Oxford. The deadline to actually sit these tests is 20 January 2018 for most universities or 20 October 2017 for Oxford. Therefore, you still have time to book and practise for the test.
If you would like some more information on the LNAT and how to prepare for it, have a look at our LNAT page here: https://www.thelawyerportal.com/free-guides/lnat-guide/
Once you think you’re ready and have all the information you need, you can book your test through the LNAT website: http://www.lnat.ac.uk/
Hope this helps!