It's not really clear what you are trying to do.
Your question seems to relate to uploading a file into a Dataset in Teamcenter, but then you state that you've already done this and the microflow you show seems to be retrieving data over a relation instead.
If you want to perform an ExpandGRMRelation, you can use the provided activities in the Teamcenter Connector rather than calling the SOA
If your question relates to uploading a file and relating the resulting dataset to an ItemRevision, then you do it this way:
1. Create Dataset object locally, attach documents and call Upload File
2. Create CreateRelationInput object which links ItemRevision and Dataset objects and call Create Relation