Skyrim Script Extender (abbreviated as SKSE) is a third-party tool designed for the PC version of The Elder Scrolls V: Skyrim. It is one of the essential utilities required to create, modify, or update mods (modifications: custom versions of the game tailored to the player's preferences). If you plan to edit Skyrim on your PC, you can do so after installing SKSE.
Steps

Download SKSE. You can download Skyrim Script Extender (SKSE) from the developer's official website. Do not download the "installer program"; instead, choose the "7z archive" file. The installer may cause issues, and the process tends to go smoother when you manually install the file.

Download and install 7-Zip. This is a free compression tool that can open .7z files. You can download it from 7-zip.org.

Extract the SKSE Files. After installing 7-Zip, right-click on the compressed folder and select 7-Zip → Extract Here. A new folder will be created in the same location as the extracted files.
Locate the Skyrim Folder. First, you need to find the Steam folder because you cannot install Skyrim without the Steam platform. The most common default installation directory is:
- C:\Program Files\Steam\steamapps\common\skyrim\

Open the Extracted Folder in a Separate Window. Now you will have two folders: one for Skyrim and another for the SKSE files.

Copy all .dll.dll and .exe files from the SKSE folder into the Skyrim folder. These will be all the SKSE files except for two folders.
- If prompted, select to overwrite or replace all existing files.

Open the .Data\Scripts\ folder in both the Skyrim and SKSE directories.

Copy all .pex.pex files from the SKSE folder into the Skyrim Scripts folder.
- If prompted, choose to overwrite or replace all existing files.
- The remaining files can stay as they are. These files are only necessary if you intend to recompile your mod from scratch.

Return to the Skyrim game folder.

Right-click on .skse_loader.exe and select "Create Shortcut".

Drag the shortcut to your desktop.

Launch Steam. The Steam platform must be running in order to start the modified version of Skyrim.

Double-click the shortcut .skse_loader.exe to launch Skyrim. You can now download and install mods that require SKSE for Skyrim.
Advice
- Modifying the game scripts can lead to errors or damage saved files, so it is important to back up your game progress before making any changes.
