Hello Tanaya ! you dont have to unless you have not selected any of the freeze/float/slide option after you have been alloted a college in first round

You just have to visit the ARC centre once just after the round when you were assigned a college for the first time and chose Freeze/Float/Slide. The option you chose will be used as default for the subsequent rounds. If you wish to change this option to something from the other two, you will have to revisit the ARC centre.