the dlls you will find them inside your SDK folder....
"Download the Steamworks SDK from the Steam partner site. Make sure the version matches the one specified for the Greenworks plugin version. From the redistributable_bin folder, copy the appropriate file for the platform. For example add steam_api.dll to package.nw for the win32 build, steam_api64.dll for the win64 build, etc."
step1: place your SDK 1.50 inside documents !
step2: open your SDK 1.50 then open redistributable_bin folder
step3: discover whats your operating system
step4: copy the file apropriate to your operating system (steam_api64.dll or steam_api.dll)
step4.1: open => public/steam/lib and select either sdkencryptedappticket64.dll or sdkencryptedappticket.dll based on your operating system.
ps: put these files inside package.nw inside your game folder (you downloaded from construct 3)
step5: you know the zip file you downloaded from Construct containing your game?
extract it into the content folder of your new SDK 1.50
step6: make sure you open package nw inside your content folder containing your game and place the dlls inside it.
step7: you know the NW.JS you downloaded from NWJS? (Every NWJS is an executable)
you can even right click it and you will notice your NWJS has an .exe extension.
step8: Inside your content folder containing your new game with dlls inside the package.new make sure you remove the .exe from it or just delete it.
step9: (VERIFY you no longer have the .exe of your exported game and then move your new NWJS 0.60 inside your content folder containing your game)
step10: Create a steam_appid.txt file and inside it write your appid frm your game.
step11: make sure your depot_build.txt inside your scripts folder contains everything you need to export your game on steam including the new path inside "LocalPath".
step12: make sure you replace all your appids and depotids with your games appids and depotids. inside the script folder... there is a youtube video for it (Steampipe tutorial)
you will launch your game on steam...
make sure that on steamworks page where you have the path to your executable you add "in-process-gpu" inside arguments right below your game.exe also make sure you rename your exe path as the same as your games path....
take care!
Hope I was usefull!
=)