Maybe you should read the Xilinx documentation, it states clearly how to initialize the content of a ROM using the block memory generator. Look for PG058.
If I read it and then post the relevant information, it just means next time you won't read the documentation and will keep posting questions clearly answered in the documentation.
You know Xilinx includes a program called Xilinx Documentation Navigator (installed by default), which makes it really really easy to search all their documentation for stuff you may have questions about.