For the given CRC polynomial the CRC generator will be of 4 bits as 1011.
Now, we have to put (4-1)=3 bits of 0's in message. hence message will become now, 11011011000.
Then we will keep on taking EX-OR between the above message and CRC generator until we get less number of bits than in CRC generator(4) by taking leading 1. then last 3 bits will be actual CRC.
Finally we have to replace that dummy zeroes with this 3 bit CRC.
this whole thing is for sender side.