You can find the human insulin gene sequence at NCBI:

https://www.ncbi.nlm.nih.gov/gene/3630

UniProt yields more information on the protein:

https://www.uniprot.org/uniprotkb/P01308/entry

The protein is processed by proteolytic cleavage, splitting off the signal sequence, a pre-peptide and an internal peptide, so that mature insulin consists of two chains with two inter-chain and one intra-chain disulphide bridges.

Two main strategies can be used: either produce native pro-insulin and process these in vitro to get native insulin, or produce the two mature chains separately and after purification, refold and oxidise to produce insulin.

Just Google "recombinant human insulin production"

You can find various published procedures for insulin production:

read a few recent review articles e.g. in https://academic.oup.com/edrv/article/42/3/374/6042201 or

http://www.bmrat.org/index.php/BMRAT/article/view/692

and follow the references to the corresponding primary publications, e.g.

in bacteria:

Article Expression and purification of recombinant human insulin fro...

Article A novel and more efficient biosynthesis approach for human i...

or yeast:

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0167207&type=printable

or even in transgenic plants.