1Dx1D vs 2D matrix, Modelsim error

The wizard will generate you a VHDL file and a component declaration you can copy/past into your design. You can use the project navigator window to then double click on a fifo to re-open the megawizard.

But personally I never use the megawizard. If I need a mega function I just instantiate it directly. That way I have much greater control and can use my own generics to re-configer it at compile time. if you go into the help -> contents -> using altera megafunctions -> megafunctions/LPM you get the whole list. In individual megafunctions, parameters are just generics and the rest should be self explanitory.

Edit: I dont like using the megawizard for simple things like altsyncram or dc/scfifo. But for much more complex things like DDR controllers its fine.