How to encode a message to MD5? I have faced a problem to understand MD5 algorithm.My question is weather the original input message is converted to binary value in MD5 before using the input message as parameter in four Feistel permutations FF,GG,HH and KK?

In order to understand my question here is an example.
If the original input message is 'amrasobaiatel' my question is that weather the message is converted to binary value such as '00010000000000' before padding and appending the 64-representation of the length of the input message?

If the answer of my question is 'yes' then my another question is that how can we convert the original input message into binary value?
MD5, like most cryptographical algorithms, takes inputs which are strings of bytes (actually, bits, however we rarely need to hash an arbitrary bitstring).  So, yes, to hash a string with MD5, you need to convert that string into a series of bytes somehow.

As for how you do that, well, for a string like 'amrasobalatel', the most common transform is to take the ASCII encoding of that string; however there's no reason you couldn't use UTF-16 or EBCDIC...