These two tutorials cover current versions of Fritzing:
I lately learned there aren’t links to the videos in Old_Grey’s tutorial so you need to do a google search for the title and then they come up on YouTube.
Parts making is a complex process, and what you are trying to do is odd even for that. What are you trying to do with the logo? Obviously you want bare copper (no mask) but do you want that for only the copper of the logo (which the current process will do, although it may need super thin 8thou traces added to connect all the copper to the connection to achieve) or a rectangle around the logo with no mask on either the board or the copper (that is possible with the invisible copper trick)? I can easily enough make your logo in to a part for you using the current example (which has the logo only on the top layer) or an invisible copper implementation where the “copper” has a fill of none so no copper will appear but it will block the mask (usually used for touch pads.)
Peter