There is NO direct way to do this.
dblp always indexes the tables of contents of complete proceedings or journal volumes in bulk. The necessary meta data for each volume is obtained by us directly from the publisher of a volume or the organizer of an event. For us, this is a more productive use of our very limited resources. Entering scattered bibliographic records is much more time-consuming. For dblp users, this policy makes the bibliography more predictable.
Also, there is no public HTML form to enter bibliographic records because there would be a too high potential for misuse, fraud, or vandalism. We take the quality of our data very seriously and, hence, we need to control, redact, and (possibly) correct all the data items that are included into dblp.
If you find that there is a conference series or a journal missing from dblp that is of general interest to the international computer science community, then you can send your suggestion (ideally accompanied with an URL on where to find metadata and further information) to firstname.lastname@example.org. Just please understand that we don't have the capabilities to reply or follow-up on all of the many mails we receive every day.