How do I authorize ArcGIS license in MIKE URBAN as concurrent use? 

You have to go through the following 5 steps - the detailed authorization procedure may be downloaded here

#01 - Import or activate MIKE license in ‘DHI License Manager’

#02 - Install ‘ArcGIS License Manager’ separately on the computer/server 

#03 - Follow the screen to authorize ArcGIS concurrent use license using EFL code (Fig. 1 - Fig. 3)

Fig. 1 - Choose the right version ‘10.1 -10.7’ for MIKE URBAN

Fig. 2 - Choose to authorize code using the Internet 

Fig. 3 - Enter the code and the number of license  

#04 - Continue to authorize the extensions showing as below (Fig 4):

Fig. 4 Enter the EFL code for extensions and the number of license 

#05 - Connecting to ArcGIS License Manager from local PC (Fig. 5) 

Fig. 5 Enter the server name or IP address from local PC

Installing and Authorizing ArcGIS Network. With MIKE Software on a Server – Recommended setup