It's complicated to get your head around but if you look at a binary to hex conversion chart you should understand. Always work backwards, its not easy to explain but hex is basically 0-9 then A-F. They both have the same value so if you look up the chart they should match up.

C=1100 etc.

Kind of hard for me to explain this but I gave it a shot haha, hopefully someone else knows better than me. You convert each 4 digit binary into its hex.

GT pretty much explained it but yeah the hex system has 16 digits, the extra needed 6 digits are represented by the first 6 letters of the English alphabet. Hence, hex digits are 0,1,2,3,4,5,6,7,8 and 9. A,B,C,D,E,F. This number system is the most commonly used in mathematics and information technologies. I.e. in html programming colors can be represented by a 6-digit hexadecimal number: FFFFFF represents white, 000000 represents black, and so on.