[SDF- 85236] How to customize the portal homepage

[SDF- 85236] How to customize the portal homepage

How can I add a button next to all other buttons for all our instances to another weblink? 
Explanation : We have a (ManageEngine) ICT helpdeskbutton, a (ManageEngine) HR helpdeskbutton, and several other helpdeskbuttons but we need also a button to enter the webpage of the application for the technical support complete with a separate icon.  
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