You know when you read a book and have no idea what's going on in the first chapter or so beyond what's immediately told to you, eventually understanding the setting and plot as you progress through it?
That's how DAI is. The first few hours is rather hectic, so make sure to read the codex (The DAI encyclopedia) to understand what's going on if you haven't played previous games. The entries are added over time so you never feel overwhelmed and they are often fun to read.
The combat system is a little unfriendly at first at higher difficulties if you're a newcomer so I suggest sticking to Casual and avoiding the tactical camera.
Throughout the first portion of the game, you receive tasks that essentially introduce you to 90% of the game's systems so just follow what's given to you in the journal.
Since this is an RPG, make sure to talk to people to get to know them, receive information and opinions, and interact with them.
It's a relatively complex game on the surface but it all melds seamlessly as you play it personally. 