Scroll down to "Connected YouTube Channels" on your settings page.
Click on the green button "Connect a YouTube channel" and follow Googles instructions to select the channel you wish to connect.
If your channel already exists on VlogTrends click "Claim" otherwise click "Add and Claim".
Your channel should now be listed on the settings page under "Vlogging For".
You can also find it through the search function or through the "My Vlogs" menu item in the top navigation bar.
When viewing your vlog on VlogTrends, click on "Manage" to manage your vlog.