How to write using TeX

I’ve downloaded MiKTeX as I’d like to write a Mathematical document using it (I’ve had some basic experience using LaTeX on the Maths Stack Exchange page as it requires everything like equations to be written using LaTeX I believe) but I’m not very good at computers and now I’ve downloaded it I don’t know where to go from there. The download seems to have 1k+ folders and I have no idea where to go. Do I use a Word document and then somehow convert to TeX or does TeX have a special writing template I can go straight to to type in?

Thanks.