Add new partner to llp

Information: LLP is incorporated in Feb'19 with 3 partners. LLP agreement (form 3) is yet to be filed as 30 days is not elasped. Meanwhile they want to add another partner to the said LLP.

Query: Should we file form 3 1st with existing 3 partners, then filed form 4 for adding partner, & again file form 3 for the changes mentioned? Or we can file form 4 adding the new partner with the mutual consent of all the exiting partners & then file form 3 with details of 4 partners.