I am trying to complete my very first salesforce hands-on training module and I am already stuck... Nice
https://trailhead.salesforce.com/trails/force_com_admin_intermediate/modules/point_click_business_logic/units/formula_fields

1. From Setup, open the Object Manager and click Opportunity.
2. In the left sidebar, click Fields & Relationships.
3. Click New.

There is no "New" button.  What am I missing?