[Koha] importing MARC21 records

Hi, We are currently using concourse and i tested importing MARC records from it to KOHA 3. When i search in opac, there are results which means the import was successful, but OPAC says holdings (0). I asked this question in IRC and they told me about 952 tag. But don't know how do map or do it? Another thing is that the barcode from concourse was not properly imported into koha, which mean in koha, barcode field is empty. Can somebody assist me pls. Thanks. Edward TH