I have a CSR so may not be same but presume its similar as also dry sump Duratec,
I have a catch tank to catch oil from breather, guess you have also. So is the catch tank empty or with just a small amount in, if so stick a piece of tape to catch tank and mark oil level, add between 250ml to 500ml of oil go for a quick drive to bring up to temp, make sure you have a reasonably "spirited" few minutes, check catch tank, if no oil blown into catch tank add another 250ml to sump , another quick drive and repeat until some oil blows into catch tank. at this point I left the car for 24 hours then using long dipstick checked oil level in sump and notched the dipstick to give oil level for my car, if normal driving bung in 250ml or so every 500miles, check catch tank levels every so often, normaly when car has been standing for a day or so you can check oil in sump to get an idea of oil level, pretty quickly you will get a feel for how your driving style uses oil, obviously track days will use more oil so check after every session. empty oil from catch tank occasionaly.
HTH
Tim
CSR 200 Aztec and Black