Google announced the launch of a new upgrade center for upgrading AdWords accounts to Enhanced Campaigns. Accessible from the left-hand navigation bar on the Campaigns tab, the upgrade center lets advertisers managing several campaigns perform bulk upgrades to multiple campaigns simultaneously and merge selected campaigns in a few simple steps. The center lets advertisers upgrade several campaigns at once and merge them together.
In a blog post, Google explains how to use the tool:
The upgrade center will roll-out to advertisers over the next few weeks.

