Learn Farsi: من عطر را روی مچ خود بوییدم.

While some sensory experiences in Farsi use impersonal structures (like az bish khosh-am mi-âyad), actively smelling or sniffing something on purpose uses the regular active verb buyidan (to smell). Because you are intentionally smelling the perfume here, you are the direct subject, so it conjugates normally for "I" (buyidam).

Why use khod (self) instead of just adding the "my" ending to make it moch-am?

You absolutely can say moch-am (my wrist)! However, Farsi frequently uses khod (own/self) when the owner of the object is the same as the subject of the sentence (I). Saying moch-e khod translates closer to "my own wrist" and sounds very natural, especially in written Farsi.

Does râ always follow the object immediately?

Yes, râ must come immediately after the specific direct object (and any adjectives attached to it). Here, the object is simply 'atr (the perfume). By placing râ right after 'atr, the sentence clearly marks what is being smelled, before moving on to describe where it was smelled.

How are the words ruy (on), moch (wrist), and khod (self) connected when spoken?

They are linked by the hidden "e" sound called the ezafe. You pronounce this chain as ruy-e moch-e khod. This linking vowel works just like when you connect nouns and adjectives, but here it connects a preposition to a noun, and then that noun to its owner.