ARF and WRF files are both recordings used with Cisco's WebEx program. The data they contain is the same: audio and video recordings that can easily be converted into other formats. The difference between the two is in their origins. ARF files are those you download online, whereas WRF files you make yourself. Because all the file properties are the same, however, converting ARF to WRF is simple.
Open the ARF file you downloaded in WebEx.
Select "Save As" from the File menu.
Select WRF as the format, then click "Save."