Installing a second ssd. Problem/

I wanted to install a second ssd, but when I opened the lid, I saw that the expansion slot was occupied by the system ssd. What to do?

Hello, please check the position of the red circle in the picture, open the bottom case of the machine, you will find an SSD slot, thank you
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The second slot is free, but the body is sealed with a factory sticker. If I move the factory SSD to a different slot, will there be a problem booting Windows?
Which interface is supported: SATA or PCIE?

Hello, the interface inside only supports the PCIE protocol, thank you

Unfortunately, this is not written in the manual. Thanks!