Software practitioners find it challenging when they are asked to adopt Agile ways of sizing and estimation of software which is yet to be developed using Agile methodologies. At Wipro we encountered the same challenge, Among several approaches that we tried for Agile estimation, we are sharing the one that is well-received by practitioners from conventional backgrounds. We found a remarkable improvement in the estimation capability of a team as we adopted this approach for a first-time agile team. This paper elaborates on lessons learned through a case study to develop step by step approach for addressing the Agile estimation and sizing challenges encountered by first-time Agile teams.