Я скачал его на ноутбук, но мне нужно установить его и на телефон.

I downloaded it on my laptop, but I also need to install it on my phone.

Breakdown of Я скачал его на ноутбук, но мне нужно установить его и на телефон.

• я: I
• телефон: the phone
• и: and
• на: on

Questions & Answers about Я скачал его на ноутбук, но мне нужно установить его и на телефон.

Why does the sentence use скачал (perfective) and not скачивал (imperfective)?

Скачал is perfective and presents the download as a completed, one-time result: I downloaded it (it’s done now).
Скачивал is imperfective and would usually mean a process/repeated action/background: I was downloading it / I used to download it / I tried downloading it. In this context, the speaker is talking about having the file/app already on the laptop, so perfective fits best.

What case is его, and why is it его twice?

Его here is the 3rd-person pronoun in the accusative (for animate/inanimate it looks the same as genitive in this form). It functions as the direct object of both verbs:

• скачал его = downloaded it
• установить его = to install it
  Repeating его is natural and clear, but in casual speech the second one can be omitted if it’s obvious: …но мне нужно установить и на телефон (still understandable, just slightly more elliptical).

What does мне нужно literally mean, and why isn’t it я нуждаюсь?