If your drone has one or more motors which are spinning the wrong direction, there are two options two options to reverse the motor direction. For our purposes here, please note the motor/ESC's identifying number:
Method 1 - BLHeli Software
You can reverse the direction of any individual motor using BLHeli Suite software on your computer. There are two main versions of BLHeli Suite described in detail below. General information on BLHeli Suite here:
https://github.com/bitdump/BLHeli
https://www.youtube.com/watch?v=w-V0BNux-Pw
BLHeli32 Suite - For 32-bit Emax BLHeli ESC's, such as those in the Buzz, Mini Magnum 2.5, Mini Magnum 3 (e.g. BabyHawk R 4", Hawk Sport, Hawk Pro). Download here (select the latest "BLHeliSuite32...." as appropriate for your Linux/Mac/Windows [not specified] computer):
https://www.mediafire.com/folder/dx6kfaasyo24l/BLHeliSuite
After installing/opening the appropriate BLHeli32 Suite, go to the top, Select BLHeli_32 Interface, make sure it is on option M, Betaflight/Cleanflight bootloader. With the propellers removed from your drone (for safety), plug in the flight LiPo battery. Then select the right COM port at the bottom (same one as you would use for Betaflight), hit Connect, and then hit Read Setup. See the Example, below, for how to reverse a particular motor/ESC.
BLHeli16 Suite - For all other EMax BLHeli ESC's. Download here:
http://www.mediafire.com/file/1tn449x6815upat/BLHeliSuite16714901.zip/file
After installing/opening BLHeli16 Suite, go to the top, Select Atmel/Silabs Interface, make sure it is on option E, Silabs/Cleanflight bootloader. With the propellers removed from your drone (for safety), plug in the flight LiPo battery. Then select the right COM port at the bottom (same one as you would use for Betaflight), hit Connect, and then hit Read Setup. See the Example, below, for how to reverse a particular motor/ESC.
Example - If you have motors 1 and 4 spinning the wrong direction (needing to be reversed):
Go to the ESC numbers to the right of the Connect/Disconnect button, and deselect all except for 1 (i.e. only keep 1 selected/highlighted/colored). Go to Motor Direction and move the slider from Normal to Reversed (of, if was Reversed, then to Normal). Then click Write Setup button.
Go to the ESC numbers, select 4, and deselect others. Go to Motor Direction and move the slider from Normal to Reversed (of, if was Reversed, then to Normal). Then click Write Setup.
After, click Disconnect and unplug the flight LiPo battery.
Method 2 - Swap Wires
Alternatively, depending on your drone, you may swap any two of the three motor wire positions at the ESC's pads. This is generally limited to motor wires which are soldered directly to the ESC (i.e. no motor wire plugs/connectors).