To add custom fonts to your Shopify Website you need to follow few simple steps:
Go to content on the left in the Shopify dashboard and click on files
Click on the upload file button on the top right corner and upload the font file with any of the extension either OTF/TTF
Once the file is uploaded copy the link and now again go the shopify main dashboard again
Click on online store and then go to edit code
Open the main CSS file, in most of the cases it should be “base.css” but check on google if that is not in your case.
Now add the following code and replace the font name with the font that you uploaded and replace the font URL with the link you copied from the files when you uploaded the font