Mapbox's APIs live at https://api.mapbox.com. The token goes in the query string as access_token. Coordinates are longitude first.
Copy your default public token (starts pk.) from your Mapbox account. In the examples it's written {{MAPBOX_TOKEN}}.
Full reference: https://docs.mapbox.com/api/overview/
Geocoding API v6.
curl "https://api.mapbox.com/search/geocode/v6/forward?q=1600+Pennsylvania+Ave+Washington+DC&limit=1&access_token={{MAPBOX_TOKEN}}"
curl "https://api.mapbox.com/directions/v5/mapbox/driving/-122.42,37.78;-122.27,37.80?overview=false&access_token={{MAPBOX_TOKEN}}"