Launch Wrye Bash. Click to "Installer" tab. Drop the compressed package file or mod package directories to "Installer" window.
Click its mod package in the package lists in "Installer" tag.
If installing mod package has Wizard.txt, right click its package and click "Wizard". And it start up the BAIN Wizard installer.
If some sub packages exists in the "Sub-Packages" on the right window, select the sub package the player wants to install according to the documentation such as readme files. If some esp/esm files exists in the "Esp/m Filter" on the right window, select esm/esp files the player wants to install according to the documentation such as readme files. Select the package, and right click its package, and click "Install". And it will complete install.
Click "Mods" tab and click installed esm/esp file to activate its esm/esp as needed.
Then, find the mod you want to download. Click the download link, open it as winrar, wait for it to finish. Double click it then hold your mouse over everything there so everything gets "activated".
Next click "extract to", click this "Program Files (x86)" > "Steam" > "Steam Apps" > "common" > "Skyrim", click once (don't double click) on "data", then click Ok.