Scott explains that buy-in means having your organization in alignment. This means all levels of the organization are working together and have the same goal in mind. By getting leaders to agree what the problems are, what success looks like and who is accountable for those solutions is an integral part. Also, appealing to the rational self interest of employees is important, as well as awarding and recognizing employees for their hard work.
This podcast is also available as an article: Obtaining Buy-In From All Levels