The rear derailleur has been adjusted in the factory but due to parts movement during shipment, slight re-adjustments might be necessary. Derailleur adjustment is done by barrel adjuster and “H” and “L” screws as shown in photos below.
The process is explained in the video below in detail: https://www.youtube.com/watch?v=UkZxPIZ1ngY
NOTE: Please note as the derailleur is already adjusted in the factory, any issues in changing gear between gear #2 to #6, should be easily solved by turning the barrel adjuster in the right direction (As per instructions in the video above). After the gears are smoothly changed between gear #2 to #6, please test gear #1 (the largest cog) and #7 (the smallest cog). If you have any issues on gear #1, you need to adjust the “L” screw and if you have any issues on gear #7, you need to adjust the “H” screw as explained in the video above.