Starting IsoMEP you will find options to choose the type of Dimension and the offset relative to the element to place the dimension, if you set the offset with "0" value, IsoMEP will calculate the perfect offset for the element to place the dimension.

After that, you just need to select all the MEP elements to dimension: pipes, ducts, cable trays or conduits. 

Wait some seconds and feel the relief of doing hard work in an easy way!!

The installer that ran when you downloaded this app/plug-in from Autodesk App Store will start installing the app/plug-in. OR, simply double-click the downloaded installer to install the app/plugin. You may need to restart the Autodesk product to activate the app/plug-in. To uninstall this plug-in, exit the Autodesk product if you are currently running it, simply rerun the installer, and select the "Uninstall" button. OR, click Control Panel > Programs > Programs and Features (Windows 7/8.1/10/11) and uninstall as you would any other application from your system.

Some users behind a Firewall or proxy may have problems activating the add-in. Please follow the instruction on the link to solve proxy problems.

https://knowledge.autodesk.com/support/autocad/troubleshooting/caas/sfdcarticles/sfdcarticles/AutoCAD-requests-to-Autodesk-servers-blocked-by-proxy-servers.html