On mobile click on head and shoulders in top right hand corner.
Click on messages
Click on compose message
Enter into send to the members yes crowd name exactly as it as it appears.
Another way is once you are logged in click on the user's name you wish to pm and then you are able to click on send private message from their profile.
__________________________________________________________________________ I’m a Yes Crowd Champion (not an Optus employee). I share my knowledge on Yes Crowd on a voluntary basis. If I answered your question, please mark it as a Accepted Solution. If I helped you out, hit that Kudos button