Learn Russian: Ты уже получил посылку сегодня? - Did you already receive the parcel today?

To say "from my friend" (a person), you would use от + Genitive: от друга. To say "from Moscow" (a place), you would use из + Genitive: из Москвы. So you could ask: Ты уже получил посылку от друга из Москвы?

Why use the perfective verb получил instead of the imperfective получал here?

The word уже (already) shows that we are asking about the successful result of the action. When you want to know if an action is completely finished and the result is achieved (the parcel is in your hands), you use the perfective aspect.

Why is the word for parcel spelled посылку here instead of посылка?

The dictionary form is посылка. Because the parcel is the direct object receiving the action of the verb (the thing being received), it must be in the accusative case. Feminine nouns ending in -а change to -у in the accusative, making it посылку.

Can I change the word order and put сегодня at the beginning?

Absolutely! Russian word order is flexible. You could say Сегодня ты уже получил посылку? Placing сегодня at the end of the sentence simply puts a little extra conversational emphasis on the fact that we are asking about "today."