Gitlab looking as old UI

Hello, my Gitlab is looking as old UI (no sidebar and menu shows on the top).

I just installed it on a, Ubuntu 16.04:
GitLab 9.0.2
GitLab Shell 5.0.0
GitLab Workhorse v1.4.2
GitLab API v4
Git 2.10.2
Ruby 2.3.3p222
Rails 4.2.8
postgresql 9.6.1

Do you know what can I do to switch to the new UI with the sidebar?

Thank you!