When you want to transfer a campaign from one user to another you go to the campaign page. Here you choose the campaign and then click on Transfer Campaign.
Then you choose if you want to copy the campaign or move it to a different account. You write the email of the user you want to transfer the campaign to and click on the OK button.
If someone transferred a campaign to you it will appear a small red number on top of your user name. The number shows how many campaigns you have pending.
You then click on Pending/Approve Camapign to get to the page where you approve the campaign.
Click on the Accept button to accept the campaign.
You will now find the campaign under the page My Campaigns page marked as a Transferred campaign. This will not be visible when distributing.