In Discover you can like the part of someone's profile that stands out to you the most by tapping on the red heart on any of the 6 photos or 3 prompts. Then, confirm by tapping Send Like.
You also have the option to Add a comment (users who leave comments are 3x more likely to receive a response!)
When someone likes your profile, you'll see that in your Likes You tab.
To match and begin chatting, tap your Likes You tab in the navigation bar at the bottom of the screen. That person will disappear from Likes You and appear in Matches.
To skip a profile in Discover tap the black X at the bottom left of the profile.
To permanently block or report a profile in Discover tap the three dots at the top right of the profile and select unmatch or report, respectively.