Hey Navin,
Cool thanks for clarifying. I had never heard of Media Platform but looks like an interesting vendor.
Unfortunately you are going to have a lot of manual work if you are using a vendor without an integration to do webinars with Marketo. The list uploading etc. is a time killer.
There may be someone clever who has figured out a way to get these systems to talk to each other with APIs, if Media Platform has one.
My advice would be to use a supported vendor if you can...
That being said, also post an Idea in this community for Marketo to add Media Platform to its list!