Production:
The /ch/ sound is actually a combination of the /t/ and the /sh/ sound. To make the sound, begin with your teeth together and bring the tip of your tongue to the small ridge just behind the front teeth. The corners of the lips are pulled together so the lips pucker. This is a voiceless stop consonant, which means that the sound comes from air that travels through the mouth and is stopped by the tip of the tongue touching the roof of your mouth behind your teeth before it is released from the mouth. Your vocal cords do not vibrate during the /ch/ sound and you will not feel your throat vibrate if you were to place your hand on it. To make the /j/ sound "voice" the /ch/ sound.
Tips for producing the /ch/ and /j/ sounds: peachiespeechie.com/videos
Here are some fun activities you can do at home to practice your speech sounds!