I would assume you are using the Gas domain to model your system and try to use different Gas Property block to switch the working fluid.
For water (steam), you may be able to repurpose the default properties of the "Water Vapor" properties of the Moist Air domain or the default "Vapor Properties" of the Two-Phase Fluids domain for your Gas property table. The default fluids are water.
For methanol or any other mixture, I would suggest that you try REFPROP or CoolProp to get the property table you want. The "twoPhaseFluidTables" command can be useful for extracting a collection of properties from these two databases, but you'll need to write some script to put them in the format needed for the Gas Property block.
