Your printer should be cleaned and greased after a certain period of time in order to work properly (see the 3D Printing Handbook).

In most cases, this lubricant is not needed during the first assembly of the kit. More information, including pictures, is in the online service manual.

Note: Pre-lubricated bearings are supplied in small blue bags as shown here. If this is not the case for your printer please apply this lubricant.