Setting for Avid Media Compser

Hi, I have come back to editing with Avid Media Composer after a break of some years and I am having a few issues importing material. I would like to encode my footage from MP4 to MXF op1a which Avid should accept. I am using the pre-set DNxHD for NLEs which looks like it uses the MXF container but I can't get Avid to recognise the files. I am using the most up to date version of Avid and Media Encoder. Any help would be most appreciated.

Thanks!