If it is your server logon details you're talking about, contact your ISP or
host - they have the details.
If it's your ISP/host and they are one and the same, then most often your
internet logon is the same as your web hosting space logon.
If you're hosting with a separate provider, did you sign up over the internet,
which means you would have got your logon details by email, usually this works
with the email having an 'activation' link or something to activate the account.
Anyway, have a search for this email in your messages (if you kept it).
Or there might be a "forget password" utility on the host's site, where it can
email you your password or send you a new one.