Expert advice needed who are into CPA Ads

Alright guys,
I am planning to promote my products via CPA ads.
I sell digital products online, so that can help me to promote my website.
Now I have been working as a publisher to many cpa networks, day before yesterday CPA Lead emailed me and they asked to do advertise with their network, so I am thinking to start CPA advertisment.

But, I never did CPA ads before, they ask me to add a lead generation form and trust me I dont have any idea about it, didn't get the correct answer by doing Google search too. May be I need to hire a freelancer for it.

So, can anyone help me how can I proceed with it.?
Also, if there is any CPA owner who can brief me the procedure to become an advertiser. ( I mean the coding stuff and all)

Thanks in advance.

Guys anyone can help me with?
Still searching the answer.