Building A polysachharide

Hello all,
I want to build a polymer of repeated disaccharide unit. So please refer me any link or guide me how to do it. I tried with building unit cell and then form super cell though I don’t know if that is the correct method.

.I also would like to know why the unit cell is not covering the whole molecule? Is there any way to build an unit cell and put my molecule completely within it?
Sorry for all this naive queries.
Thanks and regards.