To upload multiple voicings in the latest My Score experience, we ask that composers complete separate uploads for each individual arrangement that they want to provide. If you have a flute arrangement, a horn arrangement, and a clarinet arrangement for example, you would want to complete 3 uploads.
Here is a link to our Uploading Sheet Music (Step-by-Step Guide) that you can reference just in case you have any confusion in the upload process! This would also be the case for uploading a vocal score versus a conductor's full score for the same piece, you can complete an upload of just the score to get that online.
If you would like us to group these products together, let us know when you've done that and we can link it with the original listing. This can be done immediately once you have finished your uploads, you just have to contact the support team at myscore@jwpepper.com or by submitting an edit via your catalog to get it completed.