Draw a molecule on the canvas by choosing buttons from the tools (for bonds and charges), atoms, and templates toolbars, including charges where needed. show the appropriate stereochemistry by choosing the dashed or wedged buttons and then clicking a bond on the canvas.

I do not think we can help you with this one. I sounds like an exercise where you use a specific program to play with stereochemistry.

Try making an molecule with carbon, and then adding some sidegroups like Bromo to it.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)