Download and unzip the software, if the latter isn’t done automatically. The resulting folder contains the main script Poserframes.jsx, the companion script ExtractPath.jsx and a folder with a number of Photoshop action sets, Poserframes2x3.atn, Poserframes4x3.atn, Poserframes4x5.atn, Poserframes6x7.atn, PoserframesSquare.atn, PoserframesAuto.atn and PoserframesAutoBurn.atn.
Quit Photoshop.
Copy the script Poserframes.jsx to Photoshop’s scripts folder. On Mac it’s in /Applications/Photoshop 202x/Presets/Scripts and on Windows 10 it’s in C:\Program Files\Adobe\Adobe Photoshop 202x\Presets\Scripts. You may have to change the permissions of this folder to copy the script there.
Start Photoshop and make sure Poserframes shows up in the menu File/Automate.
Install the Photoshop actions by double-clicking on the files Poserframes2x3.atn, Poserframes4x3.atn, Poserframes4x5.atn, Poserframes6x7.atn, PoserframesSquare.atn, PoserframesAuto.atn and PoserframesAutoBurn.atn, or by loading them in the Actions palette.
If you want to update to a newer version of Poserframes you simply replace Poserframes.jsx in Photoshop’s scripts folder with a newer version. This will not affect your script settings if you use actions or droplets to run Poserframes. However, if you opt to use the script in legacy mode (see below), your settings will be lost when you update to a new script file.