If the software is well known, then we don't usually use the word. "I use MS Word." Often the countable word "application" is preferred for a particular piece of software. e.g. "Facebook is a social media application". If you want to reference software, this is one option: "With regard to software for accounting purposes, a range of applications are available, such as Sage." If you think of software as a category word, this could help you to use it more naturally.

Usually you would put "Microsoft Word" first. However, as Microsoft Word is a name, you can put it after if the context demands it. David the programmer wrote this software. The programmer David wrote this software. The Microsoft Word software is ready to use. The software Microsoft Word is ready to use. The second form seems slightly odd when written, it looks better with punctuation or with the name in bold or italics: The new software, Microsoft Word, is quite useful.

"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.