Select a project you want to share and click on the Users icon on the project card. Upon clicking on Manage users a new window for this particular project will appear. You can add as many users as you want and assign them different roles.
If the person you want to invite is not an existing SciNote user, invite them to SciNote first by clicking on your profile photo at the top right corner of your dashboard and select Invite people to SciNote from the dropdown menu.
Type in one or multiple emails of people you want to invite and press ENTER. Finish the action by clicking the Invite users button and assigning them a user role.
Don't forget to add the new user to the project as well, after they accept your invitation to SciNote. An email with instructions on creating a free SciNote account will be sent to them.
To learn more about SciNote user privileges and roles watch this video tutorial.