Both sites take the link to the Version Control system from the META files included in the CPAN distributions. Either META.yml, or the newer META.json. (They should only differ in their format.)

As the META files are usually generated automatically when the distribution is released by the author, I am going to show you how you can tell the 4 main packaging systems to include the repository link.

In the examples I'll use the link to the repository of Task::DWIM, which is an experimental distribution listing all the modules included in a DWIM Perl distribution.

ExtUtils::MakeMaker

If you use ExtUtils::MakeMaker add the following to your Makefile.PL as parameter in the WriteMakefile function:

META_MERGE => {
    'meta-spec' => { version => 2 },
     resources => {
         repository => {
             type => 'git',
             url  => 'https://github.com/dwimperl/Task-DWIM.git',
             web  => 'https://github.com/dwimperl/Task-DWIM',
         },
         bugtracker => {
             web => 'https://github.com/dwimperl/Task-DWIM/issues'
         },
         homepage   => 'https://perlmaven.com/',
     },
},

If your version of ExtUtils::MakeMaker does not yet support this, just upgrade ExtUtils::MakeMaker. You can also write the following, if you'd like to make sure old version of ExtUtiles::MakeMaker won't freak out:

(eval { ExtUtils::MakeMaker->VERSION(6.46) } ? (META_MERGE => {
    'meta-spec' => { version => 2 },
     resources => {
         repository => {
             type => 'git',
             url  => 'https://github.com/dwimperl/Task-DWIM.git',
             web  => 'https://github.com/dwimperl/Task-DWIM',
         },
         bugtracker => {
             web => 'https://github.com/dwimperl/Task-DWIM/issues'
         },
         homepage   => 'https://perlmaven.com/',
     }})
     : ()
),

Module::Build

If you use Module::Build, add the following to Build.PL, in the Module::Build->new call:

meta_merge => {
    resources => {
        repository => 'https://github.com/dwimperl/Task-DWIM',
        bugtracker => 'https://github.com/dwimperl/Task-DWIM/issues'
    }
},

This will include a link to both the GitHub repository and the GitHub issues.

Module::Install

If you use Module::Install add the following to Makefile.PL:

repository 'https://github.com/dwimperl/Task-DWIM';

Dist::Zilla

If you use Dist::Zilla, the Dist::Zilla::Plugin::Repository will automatically add the link to your repository, though you can also specify it manually.

[MetaResources]
repository.url = https://github.com/dwimperl/Task-DWIM.git

A detailed version would include more details as in the following example. As I can see, these parts are only included in the META.json file and not in the META.yml file. In order to generate that file, you'll also need to include the MetaJSON plugin of Dist::Zilla.

[MetaResources]
repository.web = https://github.com/dwimperl/Task-DWIM
repository.url = https://github.com/dwimperl/Task-DWIM.git
bugtracker.web = https://github.com/dwimperl/Task-DWIM/issues
repository.type = git

[MetaJSON]

There are other ways to add the repository links to the META files when using Dist::Zilla.

Probably the most simple way is to use the GithubMeta plugin by adding the following line to the dist.ini file:

[GithubMeta]
issues = 1
[MetaJSON]

Why shall I add this link?

It's simple. The easier it is to send patches to the most recent version of your module, the more likely you'll get them.

Also you might have already made some changes to your module since the latest release. You might have already fixed the bug I'd like to fix. If I can see your repository we can avoid duplicate work.

Other resources

If you are already dealing with this, you could add some other resources as well. The CPAN META Specification has all that listed. If something is unclear there, just ask.

Licenses

In an other article I showed how to add the license information to the META files of CPAN distributions. If you had a public repository, it would be easier for others to send that patch too.