Put bike on centre stand on level ground
Start engine and let tickover for one minute
Turn ignition off
Watch the oil window until it settles, which will probably take about a minute
That's your oil level
Next to the oil window there are lower and upper markings on the engine casing, you want the oil level about two thirds to three quarters of the way up between the markers
Once the oil level settles, if you need to add more, do a SMALL AMOUNT at a time, then REPEAT THE ABOVE PROCESS.
Don't start pouring it in for fun, 'cos you don't want too much in there either, as that can cause other problems.
Chances are that right now you simply haven't got enough in there, i'm guessing due to you judging the oil level with a cold unstarted engine.
The window on my bike has clouded up now, so i have to fill it up by measurement alone.
Once emptied and a new filter fitted i've put in about 2.8 litres to be safe.
If you aren't changing the oil filter this time around then it's a 2.5 litre sump, so that's a good figure to start with, you can simply pour that amount in knowing you safely have enough to begin with, then top up if needed after going through the usual procedure.
Luckily i never ever have to top up between changes, and i change the oil every 4000 miles so it's not too much of a big deal, although i've decided to replace the oil filter every time now as the filters are so inexpensive.