Anybody can create an account on the login page.
You don't need to give an email address, but you can. This allows you to get a one-time login in case you forgot your password.
In the beginning you will need to fill in a captcha in order to post a group or event. This goes away after you have filled it in correctly for a few times because then the system knows that your account is by a person and not by a spam bot.
If you have given an email address, then you also get an email with a link to verify it and to get rid of the captcha straight away.
If you don't want to give your usual email address here, then check whether you can make an alias (possible for example on riseup) or make an additional account.