Can I increase the breadboard size more than full+?
Also how to import other components; like, PIC16F877A?
What is full+? To change PCB size you click on the PCB and change the size with the Inspector box bottom right.
If you can find a FZ .fzpz part or a .fzz sketch with the part, you can import it into FZ.
No, but you can duplicate the current one to make more of them to get more space for parts. The 16F877A is available in core parts, just enter 16F877A in the parts search (the magnifying glass) and it will come up.