diff --git a/docs/buildsys/koji-cbs-sigs.md b/docs/buildsys/koji-cbs-sigs.md
index bc71f03..29db277 100644
--- a/docs/buildsys/koji-cbs-sigs.md
+++ b/docs/buildsys/koji-cbs-sigs.md
@@ -195,7 +195,9 @@ What's the influence of the `tag level` mentioned above ?
    * testing : processed by signing service but packages aren't signed, and just land on https://buildlogs.centos.org CDN, so just to have publicly available pkgs that can be promoted to `release` by SIG later
    * release : processed by signing service : packages are gpg signed with SIG key, and content appear on the mirror CDN and can be consummed by all
 
-### Tags creation
+### SIG koji tags
+
+#### Creating tags
 
 To create tags, we have in place a tool that is maintained through ansible-role-kojihub and distributed on the kojihub node itself.
 That means that to be able to use it, you need to have local shell access and kick the following commands as the `koji` user , *or* eventually have admin rights and kick the tool from outside 
@@ -238,7 +240,7 @@ Added external repo centos8s-baseos to tag kmods8s-packages-main-el8-build (prio
 
 ```
 
-### Tags modification
+#### Modifying existing tags
 
 It's always possible to modify some existing tags through standard `koji` (or `cbs` alias) CLI calls.
 Example : let's add additional architectures for the Kmods SIG :
@@ -247,4 +249,20 @@ Example : let's add additional architectures for the Kmods SIG :
 for i in el8-build candidate testing release ; do koji edit-tag --arches="x86_64 ppc64le aarch64" kmods8s-packages-main-${i}; koji taginfo kmods8s-packages-main-${i}|grep Arches ; done
 ```
 
+If some SIGs want to depend on external repo, like to get all -devel packages from CentOS Stream, we can also add it :
+
+```
+externalrepo_name="centos8s-compose-latest"
+externalrepo_url="http://kojifiles.rdu2.centos.org/kojifiles/repos/dist-c8-stream-build/latest/\$arch"
+sig_tag="hyperscale8s-packages-experimental-el8-build"
+koji add-external-repo --mode=bare --tag ${sig_tag} ${externalrepo_name} ${externalrepo_url}
+koji taginfo ${sig_tag}
+
+```
+
+If external repo is already defined, we just need to add it to tags and no need to redefine it : 
+
+```
+koji add-external-repo --tag=hyperscale8s-packages-main-el8-build centos8s-compose-latest
+```