1- Find the project's .apib you want to edit the documentation. e.g.: Parking.apib (Don't edit the apiary.apib directly, it will be overwritten.)
2- Edit stuff!
3- Commit and push
4- See result on PBP's area on http://docs.pbp.apiary.io/#
Apiary has an undocumented way of merging multiple .apib files.
apiary.manifest contains an ordered list of .apib's by project on each line.
Edit the project's respective .apib and simply push it back to Github. Apiary integration with Github will read apiary.manifest and generate a final apiary.apib containing the full documentation!
You can add more files and make them appear in the final documentation by creating your new SmoeOtherApi.apib and adding its file name to apiary.manifest
NOTE: Keep format.apib and introduction.apib on the top. Don't edit the apiary.apib directly, it will be overwritten.
If you want to generate your own apiary.apib on your local machine, run run_preview.sh. It will merge the files in the order it's shown in apiary.manifest, generate an apiary.apib and host an Apiary server on port 9999 locally.(You need to have Apiary's Ruby Gem for that)