Sharing files and folders with OneDrive/SharePoint is fairly easy to do if you know where to access the settings.
Head to your SharePoint site and select the file or folder you'd like to share. Click the "share" button.
Click the drop-down arrow to select the level of access you'd like to grant. By default, documents are generally only shared internally, but this can be changed from the drop down list shown below.
From the drop-down list (accessed by clicking in point 3 above), you can specify the level of access (including the option to make it accessible to anyone with a link). You must specify a time for the link to expire and whether or not to allow the recipient the ability to edit the file (and have changes sync back to you). Note that the document/folder becomes inaccessible to outside users after the expiration date specified. (This expiration date only applies to anonymous links.)
In general, when sharing with people outside of your business, you should probably use the "specific people" sharing option and avoid the "Anyone" option. The "Anyone" sharing (aka anonymous link) is good for sending large files to people rather than emailing them, but should otherwise generally be avoided for security reasons.
When you share with a specific person outside of your organization, they will be required to create a (free) Microsoft account (if they don't already have one) in order to access the documents you've shared with them.
Once you click "Apply," a URL (web address) will be created and you can optionally email it directly from the sharing panel (or copy the link and disseminate using another method).
