First, I suggest reading this topic: I would like to ask if there are any differences between the latest version of the threshold scheme and the previous one - #2 by ypolyakov
Second, I suggest reading the README for threshold FHE encryption (https://github.com/openfheorg/openfhe-development/blob/dev/docs/static_docs/Threshold_FHE.md). The last section deals with the t-out-of-N case (Threshold decryption with Aborts).