Via the pathway itself:
On the access tab of the pathway:
Clicking the share icon, this shares with the user & sends an email (if you choose to turn this on) straight away to the user & it pins to homepage.
Add people or groups - this just gives the user/group of users access to the pathway - they do not get an email and it does not pin to homepage here you can also turn the pathway from private to open (if open = anyone who has access to your domain will have access to the pathway).
Via campaigns:
When clicking on add an action > share a pathway:
Choose your pathway to share and schedule it - they do not get an email but it does pin to homepage.
If you turn on send share email when sharing the pathway this will send an email and do all the above too (we do not recommend sending an email this way, rather you add an action > send email at the same time so you can customise it and add a nice picture as these guides suggest:
http://support.looop.co/en/articles/3496659-sharing-resources-pathways-in-a-campaign
http://support.looop.co/en/articles/3924677-why-is-it-recommended-that-you-send-an-email-and-share-content-at-the-same-time