How to show a warning before process

It's hard to know what your use case is as there is limited information here. Are you wanting to give the User the opportunity to confirm that they want the process to be initiated? (conceptually a warning usually allows you to choose what action to take next)

Hello Saurabh,

In case you are trying to warn the user before taking any action on the interface, you can use a richtext in a box layout in order to show a warning instruction.

In case you are using a link in the cardlayout to click, better try to show a Help Tooltip which would show the user what exactly it does.

In case if you have a button to click which would take to further process, try using confirmation message in the button.