opening and editing .tex files

Method 1 (long install time):
1. Download and install TeXstudio http://www.texstudio.org/
2. Download and install all of TeX Live https://www.tug.org/texlive/acquire-netinstall.html, choosing the 'simple install (big) option.
3. Open the .tex file using TeXstudio

If the above method fails, attempt method 2 (short install time):
1. Download and install TeXstudio http://www.texstudio.org/
2. Download and install TeX Live from https://www.tug.org/texlive/acquire-netinstall.html. Choose the install-tl-windows.exe file
3. Choose the 'unpack only' option and install.
4. Run install-tl-advanced.bat
5. Under basic information, click on change.
6. Select basic scheme (plain and latex) and click on OK. Under further customization, it should now show 3 collections out of 48.
7. Click on install Tex Live. This installs a basic version of TeX live.
8. To install packages you need, use TeX Live Manager
9. Open the .tex file using Texstudio

Source:
http://tex.stackexchange.com/questions/250820/installation-of-texlive-on-windows-fails

Multiple instances of TeXstudio

To have multiple instances of TeXstudio in Windows, right click TeXstudio->Properties. Go to Target, and add --start-always. Make sure there is a space between the filepath and the --start-always

Source: http://tex.stackexchange.com/questions/123660/start-texstudio-portable-in-multiple-instances