In the Gantt chart view, you have several non-exclusive options. You can either alter the task duration. You can change the task completion date. You can alter the task start date.
It is critical for the PM to make changes to the project plan, inputting actual times and tasks to record actual events and progress. It is critical for a PM to share this information with the stakeholders. It is better, by far, to control expectations than to plead for your job back because you hid anything. If it will, by golly, take ten days instead of seven, then you must make this information ‘public’ as early as possible so other people can make adjustments.
Keep in mind that if the dependency is getting in the way (preventing you making changes) then get rid of the dependency when it conflicts with the actual event. “But it doesn’t match the plan!” Life is like that. People will understand (whether they like it is another matter).