How to set up a react-native project?

Question

JavaScript

Hi everybody! Please help me deal with react-native I
have some experience with react .
At the moment there is a project that needs to be run in androidstudio
Before that, I did all the setup as facebook recommends.
And there are a couple of questions:
1. Why is the icon that the device should add always disabled
How to make it active?

2. Why when I run the command react-native run-androidgives such an error

Warning: License for package Android SDK Platform 25 not accepted.

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring project ':app'.
> You have not accepted the license agreements of the following SDK components:
[Android SDK Build-Tools 25.0.1, Android SDK Platform 25].
Before building your project, you need to accept the license agreements and complete the installation of the missing components using the Android Studio SDK Manager.
Alternatively, to learn how to transfer the license agreements from one workstation to another, go to http://d.android.com/r/studio-ui/export-licenses.html

Googled, I can't find any solution
3. Please explain in normal words what metro is and what it does?
I would be grateful for any advice on how best to get started with this.