If you still get stuck on the following screen during export...
...This means that in5 is having difficulties unpacking the image optimization libraries, likely due to permissions in your Applications folder.
You can quickly resolve it by manually unzipping the libraries.
Right-click on InDesign in your dock, and choose Options > Show in Finder.
Navigate to Scripts/in5_v3/bin/
Then double-click on any .zip files that you find to unzip them. Once unzipped, you can delete the zip files.
Run the in5 export again and you shouldn't see this "unpacking" message.