Amplitude

Please follow Amplitude's instructions here for how to access your project's unique API key and secret key. In short:

In the Amplitude Analytics web app, click Settings in the lower left navigation.
Click Projects, then find your target project.
On the General tab, copy your API key and secret key.

Regarding amplitude event ‘s user id . The details of course depends on how your product is instrumented. By default , user id is optional . Per ampitude , Using them is optional, but recommended: your product should set a user ID once a user has created an account, logged in, or is otherwise identified in your product . Here is a more in-depth look at how amplitude is tracking user

For most cases, we strongly recommend our customer to track their users . You can do so via either Identify API directly or using one of their supported sdk's