If you do not yet feel comfortable using Linux, then perhaps you better first read the page Working with the Shell and train a bit with the shell/terminal environments, so you can have a better perception of the steps shown in the pages for each version.
For the most part you have the following choices on how to install OpenFOAM 7:
- Install from Deb packages, as documented in the official instructions: OpenFOAM v7 | Ubuntu
- You can install from source, by either:
- Following the official instructions from here: OpenFOAM Source Repository
- Or by following the detailed step-by-step instructions provided in the following pages: