I leave it to you to solve that, it's very educative.
Spend 5 minutes googling the forum to find an answer.
Suppose that you did figure out how to collect the incoming string as a number, and that number was 475. Think about what these statements are going to do:
Serial.print("Frequency Set to: ");
Serial.println(v, BYTE);
The variable v is declared as an int, so it is perfectly capable of holding 475. But, you say that you want v printed as a byte (i.e. not converted to an ascii string representing the value). But, v is not a byte sized variable. You might want to experiment to see what happens when you try to print a non-byte sized variable as a byte.
Perhaps this means that you need to have a peak here:
and learn exactly what bytes and ints are and can hold.