Either you continue from the previous step, or you
Select the web resource under Registered Resources
Click Edit Resource Host...
Click Advanced Settings...
At the bottom of the page, click Add Attribute... under section Back-end Attributes.
Add a back-end attribute:
Enter guac as Name.
Use Header as Type.
Use Static Value as Source.
Choose None as Encoding.
As Value, add username, password and IP address or DNS name of RDP host:
TEXT
<protocol>://username:password@<target-server>/?<parameterkey1>=<parametervalue1>&<parameterkey2>=<parametervalue2>
this could look like:
Example
TEXT
rdp://agadmin:admi123!@192.168.1.2/?color-depth=16
or
ssh://192.x.x.x/
protocol - is one of: rdp, ssh, telnet, vnc
additional parameters following: key=value,key=value...
More details can be found here: https://guacamole.apache.org/doc/gug/configuring-guacamole.html#connection-configuration
Click Add.
Click Next and Finish Wizard.