The phrase "second instalment" simply means the second part or payment of something, especially when there are multiple payments or parts involved. Full definition
We've been waiting quite a while now to get our hands on the highly anticipated second instalment of the re-imagined South Park gaming franchise but the question is, was the wait worth it in the end? (theeffect.net)
Welcome to the much anticipated second instalment in our Greatest Gaming Soundtracks series. (ab-gaming.com)
Scream 2 — a self - reflexive sequel whose box - office success arguably had greater bearing on the decision to make Book of Shadows than The Blair Witch Project did — established what I consider two definitive rules about second instalments to which Book of Shadows actually adheres: (filmfreakcentral.net)