You need to post a little bit more information about how the data from the first simulation are saved.
Supposing that you have in Matlab.mat in the workspace and that it contains the two things you need to use: the time vector and the signal data, then you can use the "From Workspace" block to make that signal available in Simulink: http://skit.ch/nwnt A few things to consider: Although not strictly necessary, it is better if you make sure that the sample time in your "From Workspace" block is the same as the time vector in your source signal. Also if your second model will run longer than the data set you got from the first simulation, decide what behavior you want on the "From Workspace" block after the time vector reaches its end; you can either set the output to zero, cycle over, hold the final value or extrapolate it.
