FPGA and the clock

You need to look at the specific part that you are placing on your board and find out which pins are allowed to be used as clocks. You will find that you need what is called a "global clock", look through your documentation. Before you lay out a board know all your parts and what they require. Determine which signaling and power supply voltages are important and then read up on that aspect of your chosen fpga as well. You will find that logic voltage levels are in banks. Again read through the documentation a lot before you bother laying out a board. Otherwise you'll end up with an expensive paperweight. As far as clocks, if this is all new to you, I would, if you have the option use a dedicated 10 us period chip oscillator rather than using a crystal, or even a signal generator set to the proper frequency. The clock is one of the most basic signals on your fpga and if you don't have experience using crystal oscillators, avoid them for now, unless someone you trust gives you a know working circuit for it.