How do I take a screenshot of the BIOS screen on my Dell laptop?

No way that I know of, other than with a camera.   I've had to take screen shots of the BIOS and other boot screens and had to use a camera then "fix" the pictures with a photo program.

1) You can use the keyboard shortcut to take a screenshot on Dell screen.

This method is very simple. When you want to grab the Dell screen, all you need to do is to find the "Print Screen" on keyboard. 

Just press the "Print Screen" and it will create picture of the whole screen and save the image to clipboard. 

2) If you want to adjust the capturing size according to your need, you can use a one-click application FastStone Capture to help you to take a screenshot on Dell laptop.

3) To take a screenshots on Dell, you can also select the professional Apeaksoft Screen Recorder.

a. Free download, install and run Apeaksoft Screen Recorder on your Dell computer.

b. Choose the third option, "Snapshot". Capture the whatever you want to snapshot on the computer.

c. Then your mouse will be the shape of a cross. You can select the area you want.

• Grab a USB flash drive, connect to your Operating System and backup its data.
• Now format that flash drive to FAT 16/32 file system. Right Click > Format > Select File System > Click Format.
• Restart your PC and keep pressing , or whatever the specified BIOS access key is.
• Once you enter the BIOS, make sure your USB drive is detected, check boot device priority
• After confirmation, press or Print Screen (PrntScr) key to take screenshot. It will be stored in your flash drive with .BMP extension.

Note:

• The screenshot in this post are taken on a Gigabyte motherboard running UEFI Dual BIOS. These boards are notorious for having USB 3.0 problems.
• Older Intel motherboard BIOS might not support this function. You will have to use a camera.

I have found a solution but I do not know if that would work:

Step 1: Start or restart your computer, continually hit a boot menu key to open BIOS settings.

Step 2: Insert a USB flash disk to the current computer, hit F12 to capture a screenshot. The screenshot would save to your USB drive. Note: Your USB flash drive formate must be FAT32.

Tip 2: How to Take Screenshot of Boot Screen

Step 1: Before we go to the login screen, we can hit the Print Screen key to capture a screenshot.

Step 2: Paste the screenshot to a document file or text file to save it. As a result, the Print Screen key can capture only one picture one time.