Follow the instructions as documented in Running on Microsoft SQL Server 2005 up to Step 2. Then, we will need to enable the listener port necessary for Joget to establish connection to.
Step 3: Enabling TCP/IP on Microsoft SQL Server 2012
Figure 1: Sql Server Configuration Manager
Figure 2: IP2 - TCP/IP Properties under Protocols for SQLEXPRESS
Figure 3: IPALL - TCP/IP Properties under Protocols for SQLEXPRESS
Figure 4: Restart SQL Server Service for changes to take effect
Figure 5: Verify the listening port using command prompt 
Figure 6: Verify instance based on the PID