The plug basically fits in the bore that would normally house the oil pump shaft. Keep the o ring in there, or just smear with oil resistant sealant and push the plug in. This plug is retained by the blanking plug holder which bolts on to one of the original oil pump mounts.

Fill the small extra feed hole with epoxy or whittle up a tapered aluminium pin to knock in there. Bung a bit of sealant over the top just in case!