s4pe 0.4.4-beta has an inline help added that explains how to add/merge files into packages. If that is not clear enough you can post feedback on the Help file here.
Sims 4 Studio has a handy drag & drop merge .packages feature. There is a tutorial showing how to use it HERE but it's pretty straightforward:
It's nice to use this feature in tandem with Sims 4 Studio's My CC feature that allows you to browse your Mods folder, view your content in a 3D model viewer, and easily edit it (delete unwanted .packages or unwanted swatches within .packages, change tags, etc). There's a tutorial HERE that shows how to use this feature but, again, it's pretty straightforward:
Comments
This link may help
http://stinkyeggsandwichsims.blogspot.com/2014/09/how-to-combine-package-files-using-s4pe.html
http://forums.thesims.com/en_US/discussion/817478/hello-come-and-introduce-yourself
http://tinyurl.com/OneRoomOneWeek
http://tinyurl.com/rosemow
My Showcase thread https://forums.thesims.com/en_US/discussion/948861/rosemow-s-rooms-showcase
< CLICK to J0in >
It's nice to use this feature in tandem with Sims 4 Studio's My CC feature that allows you to browse your Mods folder, view your content in a 3D model viewer, and easily edit it (delete unwanted .packages or unwanted swatches within .packages, change tags, etc). There's a tutorial HERE that shows how to use this feature but, again, it's pretty straightforward: