ndSync Requirements: https://support.netdocuments.com/hc/en-us/articles/115004039003-ndSync-for-Mac#require
Step 1: Download ndSync
https://apps.netdocuments.com/apps/ndSync/ndSync-2.4.0.zip
Step 2: Go to Finder and Click on the Downloads Folder
Step 3: Right Click on the file that downloads, click open with, and then Installer
Step 4: Click Open
Step 5: Click Continue
Step 6: Click Continue
Step 7: Click Install
Step 8: Setup ndSync to Launch at Startup
System Preferences –> Users & Groups -> Login Items
If ndSync is not on this list, click on the plus side, browse to Applications, and add it.