You can’ edit the silkscreen of a part from Fritzing. You need to modify the pcb svg and create a new part. This is why there normally isn’t text in parts. You can add new text in a sketch, but you can’t remove text in a part without modifying the part. Part making tutorials that apply to current Fritzing versions are here (although it is quite complex!)
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.