The Record Hours Only setting can be found under Setup > Company Settings > Timesheets.
If you want to record the hours an employee works from day to day but aren't concerned with the specific start and end times, turning this option on can make Timesheet entry faster. Instead of entering one day at a time you can enter a week's worth of time. Turning this on will mean you cannot use the graphical Timesheets or rosters.
To enter time for an employee, click 'Add Time' in the Timesheets screen. In the screen below, select the Employee, Work (and Category/Job if applicable) as per usual, then enter the hours for the week on the appropriate days.