Click the create campaign button and select 'Boost post'.
Choose the objective for your campaign, either: Video Views or Reach.
Select your page and post you wish to boost.
The campaign name is automated and pulled from the post headline but can be renamed as you want it to appear in the campaign overview and your Facebook ad account.
Select your audience or create your own affinity audience targeting interests.
Select budget, spend and the campaign period.
Your campaign is now ready for publishing.