You can update your contact info, username, email signature, and other information under Account Settings. You can always make updates on your own account, and some users (like managers and admins) can make changes for others.
To update your own account, mouse over your name on the upper right and click Account Settings.
To update another user's account, locate them in User Search, click their name to enter their account, and click the Account Settings gear on the upper right.
Change Your Email/Contact Information
You can update or add personal information, contact information and communication preferences from the General tab in Account Settings.
Each section (like "Personal Information", "Contact Information", and "Employee Settings") has its own save button. Be sure to click the relevant "Save" button for the section you edited when you're done.
Change Email Signature
Club OS creates a default email signature for you, but you can modify it under Employee Settings.
You can also change your default event reminder preferences in this section (Def Owner Reminder and Def Attendee Reminder). These settings determine whether you and your attendees will receive automatic event reminder text/emails for events that you own, and when they'll be sent. (You can always add reminders for individual events regardless of the settings here.)
Change Username or Password
You can change your username and/or password on the Security tab of the Account Settings page. Make sure to "Save Username" or "Save Password" as needed.