Tap the 
icon at the bottom of your chart screen and start dragging the rectangle that appears on the chart. You can adjust the size and parameters of the rectangle by dragging the circles at the corners of the drawing.
Once you set the desired size, you can move the entire rectangle by tapping, holding, and dragging anywhere on the chart.
At the top of your chart screen, you will see a field displaying the number of bars and pips within the selected area 
.
If you pair the Crosshair tool with the Magnet 
and move the selected area, it will get resized automatically, attaching its sides to candles as you move it. If you deactivate the ’Magnet' icon, you can resize the selected area manually again.