Hi,
First you need to know if you want to identify sample (ex: cat or dog) or if you want to identify alleles (ex: actn3 r/x)
Try google scholar and sci hub to search for related papers
Second, you need to desing your primers. If you wish to identify samples, that's a PCR plus some sequencing (yes, 4-7e/sample, even 2.1e). If you wish to identify alleles, thats with a qPCR and it gets "expensive".
The protocol is "easy": dna extraction (look for some dna extraction columns at ebay or aliexpress, even ask for free sample.I got 100uds form a usa distributor). Then, prepare the mix is trivial (you need mg buffer, taq, primers...).
If you are looking for STR with different lenght, with a PCR and an agarose gel it should be enough, otherwise you need to use some sanger sequencing (macrogen, bgi, source biosciences... a lot of them. even research centers if you have some friend inside)
As always, if you explain more your project, we can give you a better approach