molecular biology - How to specify a promoter in de novo gene synthesis service?

I am trying to use a de novo gene synthesis service (Genscript) and one part confuses me:

Where do I pick the choice of promoter? Or is the promoter choice automatic based on my plasmid choice?

e.g. Say I want a regulable promoter (say lac induced by IPTG) how do I specify it? https://www.genscript.com/account/gene_services_gene_synthesis.html

I was given to understand in a related question that with a commercial gene you essentially just "pick the promoter you want"? Or must I somehow manually edit the gene sequence I have to incorporate the promoter I want?

How to put a gene under the control of a regulable promoter?

I can definitely email Genscript in case it is not a part of their default interface but I just wanted to verify my understanding of the matter before I do so.

PS. I even checked out Fischer's GeneArt service & even that interface has nowhere for me to select a specific promoter. Makes me wonder if I am getting the workflow wrong?