It's a white app with a red-orange flame icon. You must have Tinder installed and set up on your device in order to start chatting. It's two overlapping text bubbles in the upper-right corner of the screen. Choose the profile picture of the match with whom you'd like to chat.  New matches -- those whom you haven't communicated with -- appear at the top of the screen in the "New Matches" section. Ongoing conversations appear below in the "Messages" section. You can only chat and send messages to people with whom you've matched. It's the text field at the bottom of the screen. Use the keyboard to do so. Tap the GIF button on the left side of the field to send an animated image. It's on the right side of the of the "Message" field. When a match responds or sends you a message (or if you have a new match) there will be a red dot in the Chat icon on the main Tinder page. Let Tinder know how you want to be notified about new messages:  Tap the gray silhouette in the upper-left corner of the main Tinder page. Tap SETTINGS. It's in the right-center of the screen. Scroll down and slide Messages to the "On" (red) position. Tap Done. It's in the upper-right corner of the screen. You'll now be notified when you have new messages, even when the Tinder app isn't opened.

TL;DR in Indonesian:
Buka aplikasi Tinder. Sentuh ikon "Chat". Sentuh pengguna yang “cocok” dengan Anda. Sentuh Type a Message…. Tikkan pesan. Sentuh Send. Atur preferensi notifikasi.