What you are asking is an entire molecular biology accumulated over many decades. Could you provide more specific aim(s) of the experiments that you intend to do? What gene(s) from which stages of moth in a particular tissues? Or would you like to clone homologs of some known gene(s) in other species? Or would like to see all the gene(s) expressed differentially between two or more stages of moth development or healthy and infected moths or between two or more tissues?
If you write more in detail, you would get more solid suggestions and practical links that you could study more.
If you are looking for a specific gene, you can use pcr to multiply your target gene using specific primers. And if you are interested the expression of the gene you can analyze the mRNA. And, yes the protocol is usually present on kit manufacturer's website.