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
Rokurou	ṙo-koo-ṙo:	Japanese
Amity	AM-i-tee	English (Rare)
Gunnarr	-	Ancient Scandinavian, Norse Mythology
Connla	-	Irish Mythology
Yoan	-	Bulgarian
Glukel	-	Yiddish