The transistors are generic. If you drag one in to a sketch you can then adjust in Inspector like this
the pull down menus will set various parameters and the part number will change the part label to BC547 (for instance.) There is a search function in core parts which will find items in core parts (here I searched for transistor)
if what you want isn’t on core parts a google search of the form “fritzing part part_number” of a search in the forum search bar (which lately has been finding things google is not) will also work. Parts from the net are of variable quality and sometimes don’t work so you need to be careful. Making custom parts is quite complex, but these two tutorials cover current versions of Fritzing (many of the others are for older versions)
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.
Peter