no its not too late and its worth claiming for - You claim up to 10 years after leaving. All you need to know should be available on the ELCAS website (just google it). Hopoe you have got your paperwork - if not i dont think it should be too much of a problem
The enhanced learning credits are very useful so make sure you claim them otherwise it is a waste, as you are a service leaver you will have to contact your ELC manager on either of the numbers 01980 6 18729, 01980 6 15853 (if you were Army that is).
They are very helpful and will inform you of the correct procedure and like the posts say above you can find the information on line. As you have claimed before you will need to complete a claim evaluation form which you can now do on line before applying for your next credits and there are various other forms that you will need to provide.
Find a suitable ELCAS registered course that will benefit your chosen career path and then give ELCAS a ring on the above numbers and they will guide you.