anstellen
to employ
To employ someone as a worker in a company or organization; to give someone a job.
Die Firma wird nächstes Jahr zehn neue Ingenieure anstellen.
The company will employ ten new engineers next year.

to employ / to turn on / to line up
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to employ
To employ someone as a worker in a company or organization; to give someone a job.
Die Firma wird nächstes Jahr zehn neue Ingenieure anstellen.
The company will employ ten new engineers next year.

'Anstellen' (to employ/to turn on/to line up) is a separable verb. The prefix 'an-' goes at the end in a main clause; in subordinate clauses and in the infinitive, it is connected to the verb. In the 'zu' construction, 'zu' comes between the prefix and the verb.
Mein Bruder stellt immer die Musik zu laut an.
My brother always turns the music on too loud.
This verb changes its meaning completely depending on whether it is used reflexively (with 'sich') or non-reflexively. 'Jemanden anstellen' (to employ someone) means to give them work, while 'sich anstellen' (to line up/to make a fuss) means 'to wait in a line' or 'to behave in a complicated way'.
Die Supermarktkette stellt viele neue Kassierer an.
The supermarket chain is employing many new cashiers.
When 'sich anstellen' (to line up/to make a fuss) is used reflexively, the context helps distinguish the meanings. If a place expression follows, such as 'an der Kasse' (at the checkout) or 'hinten' (at the back), it means 'to stand in line'. If it is combined with an adverb like 'so' (like that) or 'dumm' (stupidly), it means 'to behave in a certain way'.
Für die neue Ausstellung muss man sich stundenlang anstellen.
For the new exhibition, you have to line up for hours.
The command 'Stell dich nicht so an!' (Don't make such a fuss!) is a very common idiom. You say it to someone who is behaving in an exaggerated or unnecessarily complicated way.
Komm, hilf mir, und stell dich nicht so an!
Come on, help me, and don't make such a fuss!
In the meaning of 'Unfug machen' (to cause mischief), the verb is often used with indefinite objects like 'etwas' (something), 'nichts' (nothing), or 'Dummheiten' (silly things). It often appears in the question: 'Was hast du angestellt?' (What have you done?/What have you been up to?)
Ich hoffe, der Hund stellt nichts an, während wir weg sind.
I hope the dog doesn't get up to anything while we're away.
When it is about turning on devices, 'anstellen' (to turn on) is often combined with 'Heizung' (heating), 'Radio' (radio), 'Fernseher' (television), or 'Licht' (light).
Stellst du bitte das Radio an? Ich möchte Nachrichten hören.
Could you please turn on the radio? I want to listen to the news.
to occupy / employ
'beschäftigen' and 'anstellen' can both mean that someone works at a company or organization. 'anstellen' usually emphasizes the step of someone getting a job. 'beschäftigen' emphasizes more that someone works there, or that a company has employees. That is why the words can be confused: someone who is hired is employed afterward. In job application situations, 'anstellen' often sounds more precise; when talking about the number of employees or an existing employment relationship, 'beschäftigen' fits better.

Mein Vater möchte im Herbst einen neuen Fahrer anstellen.
My father wants to hire a new driver in the fall.
Der kleine Betrieb beschäftigt nur drei Personen.
The small business employs only three people.