What steps are involved in setting up transactional replication for the first time between a publisher and a new subscriber?

You configure a distributor if one does not already exist, create a publication on the source database specifying which articles, meaning tables or other objects, should be included, create a subscription on the target database pointing back to that publication, and then perform an initial synchronization, often through a snapshot, before ongoing transactional changes begin flowing automatically.

EXEC sp_addpublication @publication = 'SalesPublication';
EXEC sp_addarticle @publication = 'SalesPublication', @article = 'Orders';
EXEC sp_addsubscription @publication = 'SalesPublication', @subscriber = 'SubscriberServer';