Re-installing removed oil tank on 115hp v4

I purchased a 1994 center console with a 115. The oil tank has been removed and the oil and gas are currently being mixed in the fuel tank. What is the process to re-install an oil injection tank? Is mixing in the tank a problem or just a hassle on my part. I am worried about the 50/1 ration being correct.

[boats.net]

You might want your Yamaha dealer to look to see what has been removed and how they removed it.