You can disable private time on the account, team, or team member levels.
In Settings → Account → Tracking, you can disable the Private time feature for the whole DeskTime account.
To do this, uncheck Enable private time.
Instead of disabling it account-wide, you can also restrict specific users or teams from using Private time.
For teams, go to Settings → Teams → Edit → Tracking
For individual members, go to Settings → Team Members → Edit → Tracking, and disable the Private time from there.
From this same page, you can also disable the option to Enable private time edits, which prevents employees or teams from editing/removing private time from the productivity bar.