Looks like it has them: how to use them depends on the language you use.
I know that, in Altera Verilog, simply stating
Word[35:0] <= Multiplier[17:0] * Multiplicand[17:0];
... would do it.
I meant that a programming language that targets this device will infer use of the multiplier-block.
The example I gave was for Verilog. What language are you using?
So you are using VHDL and xilinx: I'm Verilog and Altera- sorry.
Somewhere in the Xilinx software there must be a setting similar to: "Infer multipliers"... search for that.
There might be better places to ask this question, too. MAybe the Xilinx forums? Or here.