Settings is your hub for customizing your instance and notifications. Click on your name and there will be a drop-down called 'Preferences'.
General Settings
General settings gives you options for accessibility, tooltips, compactness, time/date settings, and print options.
Display Settings
In Display settings, you can customize the form view by turning on or off organizing sections in tabs or free form of tabs
Choose the preferred date format, compact spacing allows you to eliminate the extra space on the forms and lists and turn on help tips. You can also switch to old UI by turning off the next experience.
Theme
You can choose white or black theme for your Servicenow back-end interface.
Accessibility
In accessibility settings, you can choose the color patterns for the graphs in reports
Forms
In the forms settings section, there are a couple relevant settings. Tabbed forms allow related lists and form sections to be organized into tabs. Related list loading should almost always be selected as With the Form, but this setting deals with when lists related to the form in question load.
Notifications
Notification settings are more complicated but the most often used. There are 4 options to edit notifications settings: