Your site name will appear as a tab in the header. Access the pull-down menu under you name. From that menu, select "Manage Site". You can fill in the relevant information including the time zone that your site is in. Be sure to save the results.
Then go back to the pull down menu under your site name. Select the "Manage Users" item from the menu. This is where you can set up as many users as you want, each with a unique password and privileges that you specify. Be sure to save each use's information,
This is also the place you change any user's password.