How to charge a DPF (digital photo frame) which has a built-in rechargeable battery?

My DPF (digital photo frame) has a built-in rechargeable battery but I don’t know how to charge it.

All of the following models (ME-DPF-CC series, ME-KCF-1501, ME-DPF24MG, ME-DPF24EX) will charge via USB connection. Please connect them directly to an USB port. Charging time should take about two hours and the computer needs to be on during the time.

Please connect the device in your computer, choose the “USB Connect” option and confirm it. Your computer should detect it as usual and the program will launch. Please exit the program if you’re not using it and the DPF should start charging. ME-DPF-CC series

Please connect the device in your computer and choose “USB Charge” from the option screen. Your computer should detect it as usual and the DPF will start charging. ME-KCF-1501

Please connect the device in your computer and choose “USB Charge” from the option screen. Your computer should detect it as usual and the DPF will start charging. You should see the little battery charging status at the bottom of the display. ME-DPF24MG

Please connect the device in your computer. You will see the word “connect?” on the display asking your confirmation. Please leave it as is and the DPF will start charging. You should see the little battery charging status at the bottom of the display. ME-DPF24EX