Change the permissions of Build.PL/Makefile.PL to not-executable.
Add a META.yml to the distribution. Your buildtool should be able to autogenerate it.
Run a proper command ("make manifest" or "./Build manifest", maybe with a force option), or use a distribution builder to generate the MANIFEST. Or update MANIFEST manually.
Add a META.json to the distribution. Your buildtool should be able to autogenerate it.
Define the license if you are using in Build.PL. If you are using MakeMaker (Makefile.PL) you should upgrade to ExtUtils::MakeMaker version 6.31.
Ask the owner of the distribution (the one who released it first, or the one who is designated in x_authority) to give you a (co-)maintainer's permission.