Where does one start when programming an FPGA circuit?

Question

Is there special hardware or software to program an FPGA?

Can it be done in higher level languages?

Does running an application on an FPGA "lock it in" to that execution path?

Answer 1

Is there special hardware or software to program an FPGA?
Yes. For hardware, usually we program FPGA using a USB-JTAG programming cable. For software, If you choose Xilinx's FPGA, you must use Xilinx ISE. If you choose Altera's FPGA, you must use Quartus II.

Can it be done in higher level languages?
Two popular hardware description language VHDL and Verilog HDL.

Does running an application on an FPGA "lock it in" to that execution path?
FPGA programming is totally different to 'software programming' in high level language like c. What you have to do is telling the synthesizer how to 'make' the physical circuit. It's hard to tell in a few words. Please learn the concept of PLD(Programmable Logic Device) first.