Spanish students usually find it difficult to pronounce the spellings 'ng' and 'nk' correctly as they tend to do so like our Spanish /n/ and not like the English sound /ŋ/.
/ŋ/ is a nasal sound, which means you have to pronounce it letting the air go out through your nose and not your mouth. You have to raise the back of your tongue against the palate while making this sound.
Here you are a picture that shows the position of the tongue and a video which will help you identify and pronounce this consonant sound correctly.
Now, watch the video and do the fill-in-the-gap activity. All the missing words contain the consonant sound /ŋ/ and you can use the phonetic transcription in the 'Clue' to help you. You can check your answers clicking the KEY.