How does a space group determine crystal structure?
To build lattice you need the space group, the three unit cell dimensions, the three unit cell angles, each atom's fractional coordinates (e.g., a *.cif file overall),

Acta Cryst. B38, 598 (1982)  doi:10.1107/S056774088200346X
Ni3Sn4, C2/m, a=12.214, b=4.060, c=5.219 A, beta=105.0 degrees (others 90 degrees by default), V=250 A^3 (verify), Z=2 (formula units/unit cell)

plus

http://www.chem.gla.ac.uk/~louis/software/ortep3/ or

http://www.shapesoftware.com/00_Website_Homepage/ or

http://www.iucr.org/resources/other-directories/software?result_42405_result_page=A
the big kahuna.

For 3D visualization, if you are not practiced,
http://www.berezin.com/3d/3dprism.htm