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i am also attaching a screenshot.
Soumyodeep, you can use the appkey to authenticate to access the mashup something like this :
http://ThingWorxServer>:<ThingWorxPort>/Thingworx/Mashups/<YourMashupName>?appKey=<YourAppKeyHere>&x-thingworx-session=true
You'll need to ensure that the appKey has enough rights to access that mashup