YouTrack allows to make estimation for the tasks, features, and sprints in relative units, and this is a normal practice in Scrum. You may also wish to estimate tasks and track spent time in hours, days, etc. If so, enable time management in your project, it also enables time tracking in time units on your Agile board.
Click on the project name in Settings | Project, then navigate to Time Tracking tab, and select Enable time tracking for projectcheckbox.
Then you need to configure estimations for an Agile board. Setup the board settings (Estimation field, last line of the screenshot) accordingly, the field here one used for estimation in Time Tracking in the project settings.
When Time Tracking is enabled, and estimation field is set up, Agile board shows estimations and time spent on the board.
Estimation of each particular task can be seen on the agile board, and the total estimation is shown for each column of the agile board next to the column title:
Agile board shows also a total Estimation for each swimlane, if you are using swimlanes. Estimation for all the tasks on the board is shown next to the project title, left upper corner of the board. Estimation visualizes as a red circle if spent time exceeds the estimation, and green sectors occupy the Estimation circle proportionally to the fraction of estimated time already spent.
Please read Using Burndown chart section in Doing Scrum in YouTrack if you are not familiar with burndown chart concept and basics.
In short, you can view Burndown chart by clicking Charts icon at the Agile board.
A new burndown chart is to be displayed.
If time management is enabled in the project the Estimation field is set up in the Agile board properties, you can view the burndown chart with time metrics. Ideal burndown shows the total estimation for the current sprint, while remaining effort shows how much time is needed to complete the sprint (if the estimation was correct), and Spent Time graph shows how much time is already spent. Spent time graph is based on work items you have logged for each task (card).
Ideal burndown graph is an ideal distribution of spent time on the sprint period. It assumes you spend equal time every day on the project proportionally to number of days in the estimation. Ideal burndown assumes that you do not work on weekends.
Spent time graph is literally a total of the time spent each day on every task which you worked on at the day.
Remaining effort graph is a bit more complicated. The remaining effort on each particular day is the estimation minus spent time. However, if spent time is equal or greater than estimation (i.e., there is an overdue), remaining efforts counts it equal to estimation. Besides, if the task is fixed quicker than it was estimated, remaining effort for the fixed task counts as if it is fixed as estimated.
Effort overdue continues Remaining effort graph after the end of the sprint, and is calculated similarly to Remaining effort.