> There is an input of the action called 'Post Data' but it is a collection and I do not know how to structure it.
In general, open HTTP VBO and see how it works. (Or you can always create your own VBO)
Basically ""Post Data"" should contain one row, rest is ignored. Get Body stage builds a string from it, for each column in that row in it adds urlencoded ""ColumnName=Value"" pairs separated by &
Binary files are normally sent by browser as multipart/form-data instead of application/x-www-form-urlencoded, because latter adds significant overhead for big binary files - it looks like you'd have to create your own action for multipart/form-data, if you need it.
Nevertheless, server should be able to accept application/x-www-form-urlencoded file too, which can be sent with HTTP VBO... just be prepared that your request might end up like 2-3 times the size of the actual file.