Compilation
Using the Groups feature? Refer to this.
Using a mod manager? Read MO2 or Vortex first.
Add scripts
You have four ways to fill the list.
Drag and Drop
Drop any .psc file into the app.
Drag and drop does not work when PCA is started as administrator.
Search for files
Use the search button at the top, then select the .psc files you want to compile.
Recent files
Check the Recent files feature.
Groups
Check the Groups feature.
Any folder works
A script does not have to live in the game's source folder. PCA imports the folder the script comes from, and compiles from there, so a script kept anywhere on your disk compiles fine.
That folder also comes first among the imports: if the game sources hold a script with the same name, the one you picked is the one compiled.
Scripts declaring a namespace (Fallout 4, Starfield) are handled too.
Run
Press Start. The button is disabled while the Creation Kit report raises an error.
Warnings are shown too, but do not block anything. When both exist, the error comes first.
Each line of the list shows the result of the script, and once it succeeded, a button to open the folder the .pex was written to.
Compilation logs
The Logs button, at the bottom of the left sidebar, holds the compiler output of the run you just launched, script by script. Its colour alone tells you whether everything compiled.
Refer to Compilation logs.
Where the .pex goes
By default, into the game's Data\Scripts folder — plus the namespace subfolder when the script declares one.
Set an output folder in the settings to send them somewhere else. Refer to Configuration.