Hover your mouse over the message & in the top right corner you will see two buttons, one is copy & another one is delete.
Click the copy button & than to whoever you want to forward, go to their profile click new message & than press CTRL+V from your keyboard.
How do I do this on a Samsung S3? I was also told to press and wait for pop up box, which does n't seen to work either.
If you are playing mobile version of nords, i am sorry i will be unable to help you like this because i never played on tablet/mobile device.
I will seek for someone else who plays on mobile to answer this.