Preview Image of the 2D Library Object

[Tazo]

Hi, does anybody know how can I paste the Preview Image of the library object I made when it's 2D? Photo for example:

 

I want to make this type of the sign but when I create it the preview image is blank (white)

Operating system used: Windows 11

[Lingwisyer]

Just paste your image into the Preview Picture tab?

[Tazo]

That was the first thing that came to my mind but there's no option like that