The referendum that will take place later this year is a response to the 2017 Statement from the Heart, which asked for recognition of First Nations people in the Constitution and a process of Makarrata, or treaty. The Statement was a result of a careful process of consultation amongst First Peoples for quite some time.

The Government established a Referendum Council, which set up a series of First Nations Regional Dialogues, which were Indigenous designed and led consultations across the country. Indigenous members of the Council formed an Indigenous Steering Group. Together, in consultation with Indigenous community stakeholders and with advice from constitutional experts, they designed an Indigenous consultation process called the First Nations Regional Dialogues.
After an initial Trial Dialogue at Melbourne University to ensure the proposed format worked well, 13 Regional Dialogues were held across the country, culminating in an Indigenous Constitutional Convention at Uluru in May 2017. Each was hosted by a regional Indigenous organisation:
Hobart, hosted by Tasmanian Aboriginal Corporation (9–11 December 2016)
Broome, hosted by the Kimberley Land Council (10–12 February 2017)
Dubbo, hosted by the New South Wales Aboriginal Land Council (17–19 February 2017)
Darwin, hosted by the Northern Land Council (22–24 February 2017)
Perth, hosted by the South West Aboriginal Land and Sea Council (3–5 March 2017)
Sydney, hosted by the New South Wales Aboriginal Land Council (10–12 March 2017)
Melbourne, hosted by the Federation of Victorian Traditional Owners Corporation (17–19 March 2017)
Cairns, hosted by the North Queensland Land Council (24–27 March 2017)
Ross River, hosted by the Central Land Council (31 March – 2 April 2017)
Adelaide, hosted by the Aboriginal Legal Rights Movement Inc (7–9 April 2017)
Brisbane (21–23 April 2017)
Thursday Island, hosted by Torres Shire Council and a number of Torres Strait regional organisations (5–7 May 2017).
An information session hosted by the United Ngunnawal Elders Council was held in Canberra on 10 May 2017.
Then, a final national Indigenous Constitutional Convention was held at Uluru on 23–26 May 2017. This Convention gave rise to a national Indigenous consensus position on how Indigenous people want to be constitutionally recognised. This was an unprecedented breakthrough.

Although seven out of 250 delegates dissented, it was still an extraordinary consensus and a historic moment in Indigenous peoples’ struggle for constitutional recognition. Most the of the Indigenous advocacy of the past tended to emanate from particular regions. Never before had a national Indigenous consensus position been achieved. The majority position was powerfully expressed in the poetic Statement from the Heart.
This Statement asked for two things: a constitutionally guaranteed First Nations voice (a constitutionally enshrined Indigenous body to enable Indigenous people a fairer say in decision- making with respect to their rights) and a Makarrata Commission to oversee agreement-making and truth-telling about history.
It is this long, careful process, culminating in the Statement from the Heart, that lies behind the proposal that will be put to the Australian public in a referendum later this year.

Material taken from https://law.unimelb.edu.au/__data/assets/pdf_file/0007/3230377/MF19-Australia-paper.pdf