I have a computer that comes with an APU(AMD A4 6300) can I replace it with a CPU(AMD FX 8350 black edition)?
You will need to refer to the motherboard manual for your system, which will list out what processors are supported.
The A4-6300 is Socket FM2, while the FX-8350 is AM3+, so no. As for your upgrade options, what @ray_m said.
If you provide us more information about your motherboard, we will tell you more