Once you are done testing your program with the simulator, click on the download button:
 

Now your software is in the files of your computer. Open your finder/files on our laptop, the program will be in your 'downloads' folder. The file you must look for is a '.hex' file.

In the files window of your computer you will see a MICRO:BIT device connected. Drag and drop your .hex file from DOWNLOADS to MICRO:BIT. See how the yellow light of your micro:bit blinks, this means the file is being transferred to your device. Cool!