We highly recommend you install the Mu Python editor. Mu has versions for PC, mac, and Linux, it is open source / free, and it is tailored to learning and microcontrollers such as the micro:bit and others.
Download Mu from https://codewith.mu. Click the Download or Start Here links there for downloads and installation instructions. The website has a wealth of other information, including extensive tutorials and and how-to's.
It would be best to plug your micro:bit into your computer before starting Mu, as the Mu menu changes depending on which board it detects on startup.
For Mu starting up in micro:bit mode, you should get a display like this.
The menu bar looks like the one below:
If you are familiar with Mu with CircuitPython, you are not seeing strange things. There are buttons on the menu that are different than when Mu is in CircuitPython (Adafruit) mode.
The first time you start Mu, you will be prompted to select your 'mode' - you can always change your mind later. For now please select BBC Microbit!
The current mode is displayed in the lower right corner of the window, next to the "gear" icon. If the mode says Adafruit or something else, click on that (or the leftmost menu icon Mode and then choose BBC Microbit in the dialog box that appears.
Mu will install MicroPython for you. It is not intuitive that it does so, but it does work.
Create a new blank file/program. Ensure your micro:bit is plugged in to your computer's USB port and recognized with Mu being in Microbit mode.
Click the Flash icon shown at left.
The text in the lower left will say "Flashing MicroPython (or untitled") to the micro:bit. The micro:bit yellow LED should be flashing during this process.
Then Mu will say "Finished Flashing" in the lower left corner of its window.
MicroPython is now on your micro:bit.
The flash drive that shows up on plugging your micro:bit into the computer will NOT change at all, re. you cannot tell if MicroPython is installed on your board by looking at the flash drive representing the micro:bit (unlike CircuitPython which changes the drive name to CIRCUITPY, this does NOT happen with MicroPython).
Loading MicroPython programs onto the micro:bit is different than with CircuitPython also. this will be explained next when we create a MicroPython program for Crickit.