I've just done this one for you - but the process is as follows:
go into the user who needs to become the author
change their permission level to be 'contributor' (this is only temporary)
save the new settings
go into the relevant initiative and scroll down the spage until you find the 'author' section
select the person's name from the list
save the new settings
once done, go back to the user who you just made a contributor, and revert them back to being a subscriber (their name still stays as the author once you've done this)
https://transitionnetwork.org/wp-admin/post.php?post=3189&action=edit
Hi I need to change the author of the above Initiative, to the Author below
https://transitionnetwork.org/wp-admin/user-edit.php?user_id=8572&wp_http_referer=%2Fwp-admin%2Fusers.php%3Fs%3Dian%2Bjackson%26action%3D-1%26new_role%26paged%3D1%26action2%3D-1%26new_role2
How do I do this please?