The instructions are in the user manual which you should download.
MSI does not include the manual, a bad decision, I think.
Here is what it says:
The usb drive should be formatted as fat32.
Updating BIOS with Flash BIOS Button 1. Please download the latest BIOS file that matches your motherboard model from the MSI® website. 2. Rename the BIOS file to MSI.ROM, and save it to the root of your USB flash drive. 3. Connect the power supply to CPU_PWR1 and ATX_PWR1. (No need to install CPU and memory.) 4. Plug the USB flash drive that contains the MSI.ROM file into the Flash BIOS Port on the rear I/O panel. 5. Press the Flash BIOS Button to flash BIOS, and the LED starts flashing. 6. The LED will be turned off when the process is comp
The usb drive should be formatted as fat32.
Be very patient during the process.
The only indicator might be a led flashing.
Do not interrupt the process; It might take 10 minutes.
A helpful tutorial:
You can update the BIOS without a CPU to make your Motherboard ready for newer Processors. Here's how to use the so-called BIOS Flashback Feature.
www.cgdirector.com
Most likely, you will not need to do this, I would install the cpu and proceed normally. Once running, I do not reflash a bios unless it contains a fix for a problem that is bothering me.
On a new build, I update to currency. If there is a problem, nothing else is iimpacted.