The transcription /kəˈlɛkʃən/ follows a General American source, and no meaningful variety difference has been identified here. The mark /ˈ/ sits before lek, so stress the second syllable. The first and last syllables use the weak vowel /ə/.
Mouth cues
Relax your tongue for the first syllable. Say a quick, colourless /ə/, barely opening your jaw.
Land on the second syllable. Press the tongue tip up behind your teeth for /l/, open into /ɛ/ as in bed, then stop the air with /k/. Make this syllable louder and longer.
Finish with /ʃən/. Round your lips slightly and push the tongue towards the ridge for the /ʃ/ in ship, then let a weak /ən/ trail off. Keep the middle vowel /ɛ/, not the weak /ə/ that starts the word; stress and clear vowels travel together here.
Say it in a phrase
She has a large collection of coins. Stress lands on -LEC-, so the sentence rhythm rises there, not on col-.
My collection is on the top shelf. If you stress the first syllable instead, it sounds like COL-lec-tion. Keep the loud beat on the middle syllable, as in /kəˈlɛkʃən/.
The collection opens on Friday. Keep -tion as one soft /ʃən/ syllable, never two beats.
A stamp collection, a record collection. Same stress every time, on -LEC-, whatever the noun before it.