To import OLM file to Mac Mail, you'll first need to convert the OLM file format to a compatible format such as MBOX or EML. Several third-party tools are available online that can help you accomplish this conversion. Once you've converted the OLM file, you can then import the resulting MBOX or EML files into Apple Mail. Alternatively, you can also use the built-in import feature in Apple Mail to directly import the OLM file. Simply navigate to the "File" menu, select "Import Mailboxes," and choose the appropriate file format (MBOX, EML, or OLM) to import your emails into Apple Mail.