1. to turn on (For “mid-sized” stuff like a TV, a heater, a washing machine. But definitely less common than "anmachen".)
Opposite (closest): abstellen
2. to make a mess, to mischief ("etwas+Acc anstellen" - Mostly used for pets or kids after they messed something up, usually with a generic word like "etwas" or "nichts". NOT with the specific deed.)
3. to join a line, to queue up ("sich+Acc anstellen"... it's the moment of lining up. Waiting in line itself is called "anstehen".)
4. to employ (Only in the sense of work employment. "einstellen" is the more common choice as a verb, but many related words are based on "anstellen". As for login, you can think of it as "activating" as well as "putting at" the machine :).)
Opposite (closest): feuern
5. to go about something in a stupid/smart/… way or to act stupid/smart/… while performing a task ("sich+Acc anstellen" - comes in combination with adjectives like smart, dumb, skilled and similar.)
6. to make a fuss, act sissy, be a drama queen ("sich+Acc anstellen" ... colloquial. Usually in combination with "(nicht) so".)
