You are moving computers, or got a new computer, and want to bring your AutoCAD workspace over to the new computer.
1. Type CUI in the Command line on the old (or first) computer and press Enter.
2. Select the Transfer tab in the Customize User Interface dialog box.
Select the workspace you want to transfer in the left pane, beneath Workspaces (example: My Workspace Settings).
Drag that workspace into the Workspaces section in the right pane.
3. You should now see your workspace listed under Workspaces in the right pane.
Select any additional workspaces you want to transfer from the left pane, and drag them here as well.
When finished, click the disk icon and save the resulting CUIX file (to) an external hard drive.
4. Insert the external hard drive into the new (or second) computer. Then type CUI in the Command line and press Enter.
5. Select the Transfer tab in the Customize User Interface dialog box.
Click the Open customization file button on the right pane (pictured to the right).
Select the CUIX file you saved to the external hard drive.
6. Select the workspace you want to transfer, and drag it into the Workspaces section in the left panel.
Click the disk button to save the transfer.
For more information, see the official Autodesk article on transferring a workspace.