"The Microsoft Word software" is probably the best one for you to use.
"The software: Microsoft Word" can be grammatically correct depending on how you say it (notice the colon). I'd say you're more likely to use that one if they don't already know what Microsoft Word is. You're first telling them that its software, then telling them its called Microsoft Word. It makes the point that the fact that its software is important information for them to know. It also carries a more formal tone, and sounds like something you might use in a piece of academic writing or a formal presentation rather than normal speech.
In the first one "The Microsoft Word software", the fact that its software is less important, tagged-on information.
Usually in general speech people would just say "Using Microsoft Word", as its so widespread that everyone knows what it is, meaning that there's no need to mention the fact that its software.