How to test frontend app step by step by scenario?

We have a web project and the main business flow is going through the chain of processes (conveyor). We don't have any automatic tests for front. So, to test we use our "hands".

What I want to do is to create some auto test that goes through every step and every window that I do always using hands from my browser.

Any suggestions?

P.S. I don't have an access to frontend app. All I have is the running app on my browser :)