Support for MathTime 1.1 and MathTime Plus fonts in LaTeX 2e is available in /macros/latex/packages/PSNFSS. Look for the files mathtime.dtx and mathtime.ins. `TeX' the file mathtime.ins to create mathtime.sty, then add \usepackage{mathtime} to your source file. Run LaTeX on mathtime.dtx to obtain the printed documentation for the package. You will also need to change text fonts, perhaps by using \usepackage{times}, and specify the text fonts encoding (e.g. T1 or LY1 or LM1). Otherwise the package defaults to assuming that you are using T1 encoding.