Learn Swedish: Sväng vänster nu.

The infinitive (dictionary form) of the verb is att svänga (to turn). To give a command in Swedish (the imperative mood), you use the stem of the verb. For most verbs that end in -a, you just drop that -a to find the stem. That gives us sväng.

Why isn't there a word for "you" in this sentence?

Just like in English, when you give a command in Swedish, you don't need a subject pronoun like du (you). You just start the sentence directly with the imperative verb, which is sväng here.

What is the word for "right" if I want to tell someone to turn right instead?

The word for "right" is höger. If you wanted to say "Turn right now," you would say Sväng höger nu.

How do I pronounce the ng sound in sväng?

The ng in Swedish is pronounced exactly like the "ng" in the English word "sing" or "swing". It is a single, soft sound, meaning you don't pronounce a hard "g" at the end.