Your username is the letter 'm' (lowercase) followed by your membership number without any initial zeroes.
If you are not a (paid up!) member then you will be unable to log in to the site
Note too that if you are a paid-up member but the Membership Secretary does not know your current email address, you will also not be able to log in
If you are a paid-up member and have kept us up-to-date with your email address then you can set your password as follows:
make sure you know your membership number(*)
your login username is the lowercase letter 'm' followed by your membership number without any leading zeroes
click on 'Log in' (top right) and then 'I forgot my password'
type in your login username (see (2) above) or your email address(*) and click the button to get an email with a special reset link
(*) if you can't remember your membership number, use your email address. The password reset email will be addressed to 'Dear m9876' where 9876 is your membership number.