for starters, you could say MATLAB is the software any engineer needs to be able to use, you can simulate almost any system using MATLAB, you want to be a DSP engineer, you need to make MATLAB your best friend, download the software onto your P.C, and use its user manual to work your way around it, its got a very helpful, 'help' function.
For becoming a good dsp engineer, you need to have all basics clear in your mind. All fundamentals to be clear. Maybe you can refer some books like Rabiner & Gold.
Matlab is a tool. It is used for matrix operation initially.But now it has been used extensively to simulate the behavior of datapaths(DSP, comm etc) as well as control paths.
To be a good dsp engineer you should read a lot of DSP books.. i recommend that you read the book "Digital Signal Processing: Principles, Algorithms and Applications by John Proakis and Dimitris Manolakis".