Where do you add client logos – Clients Carousel

Can you please tell me where to add client logo’s I have tried the following

Add short code via editor into classic mode

Added logo to post call ‘client logos’ set one image as featured image. I also tried adding all logos to a single post. I have named slug ‘client logos’ & post as client logos.I added a post category call ‘client Logos’

All I seem to get is the short code appearing on the live website.

Can someone please tell me what I am doing wrong, as I am new to web design.

Is there a specific size or name I should be using?

Thanks