The center cap should pop right off with a flat blade screwdriver. It should be metal disk covering the entire hub, the cap being held in only by metal tabs putting pressure on the inside of the wheel.
Once off you will see the hub, which will look like your steering axle hub, with a clear plastic viewing window, which you should beable to see the oil level, and if needed pop the plastic center cap (small about an inch in dia.) oil to fill if needed.
It sounds to me like your tring to get the emblem off the chrome center cap, and not the cap itself.
"It's always wrong, everywhere, for anyone, to believe anything beyond insufficient evidence" -- William Kingdon Clifford
John (N9MXX) & Derek (KC9KEM)