First upload the file you want to share to OneDrive. Next right click on the file and select Share or select the file and click Share on the menu at the top of the page. Select the option on the left to either get a link or send an email invitation. Choose the permissions (view, edit, delete, etc.) you want the person to have. Add the person's email address and click Share. If you want to generate a link click Create and copy the generated link to then forward it to the person. They'll need to login with a Microsoft account to view the files, and can create it for free if they don't have one.