Charge, multiplicity, level of theory and coordination coordinates of gold compleaxes
There are various software to draw cartesian coordinates. Gaussian has its own GaussView, for example. I believe MolView or Avogadro are also popular. You can draw the molecule in any of these, then use the export option to create your coordinate file (export to Gaussian input file or xyz file). Take advantage of the fragment options for things like phenyl ligands. Also, depending on your goals, it's sometimes helpful to align your molecular axis with a principle axis (e.g. z-axis) for easier reading later, if you're using the calculation for more than just basic output parameters.

Furthermore, you can try to find the molecule in an x-ray database and adjust the geometry yourself to approximately match, which can pay dividends later by drastically simplifying the Gaussian calculation, particularly if you are using a larger basis set. You at least want to make sure you're drawing the correct stereoisomer, because the calculation may not correct this on its own.

The charge and multiplicity are manually defined in the input file for Gaussian. I believe you type in the values in the line just above the input coordinates if I recall correctly. You should check the official manual for sample inputs. There's much more syntax to be observed for an input file.