In addition to using the "Share" tools on your crowdfund pages, you also have the option of emailing Invitations to all or selected user records on your site.
You can customize your invitation message on the template for a specific fundraiser (directs recipient to a specific page) or edit and send the "Give-All" template, which can bring your supporters to a page showcasing all of your active Fundraising Campaigns (Show All page must be enabled in Fundraising Campaigns > General settings.)
To Preview/Edit Desired Template
Go to Admin > Site Settings > Communications > Email Templates, then click on the template name you want to edit/preview:
The default template uses merge tags such as [event_name} and [organization] to allow the emails to be sent "out of the box". When editing, it is often easier to replace these with plain text than to locate the source to edit.
The preview tool is a handy way to check your message and formatting. To preview the access provided by the invitation, you'll need to send yourself an invitation from the Users page (see below) because, without a selected user record, the Preview can only send a generic "Personal Link".