sizzlin is fine - presuming you have the cart in place and can hear a sizzle?
If not you might want to blow out the atty in case there's any PG init (what they often use to ship so it doesnt dry out the wick) - unscrew it - blow through it from the end that hte cart goes into (I find this easier), and make sure the battery end is in a tissue or something.
Sizzling noises WITH a cart in place just means the liquid has reached the wick/hot coil and is vaporizing. Gurgling however is bad and then you need to blow out the atty as above

Its easy to overfill a cart when you DIY but flooding usually doesn't ruin anything (I should know I do it a lot lol)