Mutiplying a list with a function

I am absolutely new to Mathematica and am trying to solve a very basic puzzle. I am trying to multiply a function (myStepFunc) to the column values of a 2D dataset and append two of these together while also preserving the original indices.

DataFit = Append[{DataPFit[[i, k]]*myStepFunc[kyList1[k]] + DataSFit[[i, k]]*myStepFunc[-  kyList1[j]]}, {{i, Length@wlsCorrected}, {k, Length@kyList1}}]; 

What am I doing wrong here? TIA