have a fix on (something)

To have a firm, clear understanding or determination of something. I hope everyone has a fix on the material, as you'll be tested on it next week. I thought I had a pretty good fix on English idioms, but I don't understand this one at all!

Common Names:

Name	Pronounced	Usage
Besnik	-	Albanian
Young-Hee	yung-hee	Korean
Sizwe	-	Southern African, Xhosa
Yvon	-	French
Elisabeth	e-LEE-zah-bet (German), e-LEE-sah-bet (Danish), i-LIZ-ə-bəth (English)	German, Dutch, Swedish, Norwegian, Danish, English, Biblical, Biblical Latin
ElÍSabet	-	Icelandic