docs: clarify container label usage (#1319)

Co-authored-by: nils måsén <nils@piksel.se>

docs/container-selection.md

@@ -7,29 +7,53 @@ There are two options:
 
 ## Full Exclude 
 
-If you need to exclude some containers, set the _com.centurylinklabs.watchtower.enable_ label to `false`.
+If you need to exclude some containers, set the _com.centurylinklabs.watchtower.enable_ label to `false`.  For clarity this should be set **on the container(s)** you wish to be ignored, this is not set on watchtower.
 
-```docker
-LABEL com.centurylinklabs.watchtower.enable="false"
-```
+=== "dockerfile"
 
-Or, it can be specified as part of the `docker run` command line:
+    ```docker
+    LABEL com.centurylinklabs.watchtower.enable="false"
+    ```
+=== "docker run"
 
-```bash
-docker run -d --label=com.centurylinklabs.watchtower.enable=false someimage
-```
+    ```bash
+    docker run -d --label=com.centurylinklabs.watchtower.enable=false someimage
+    ```
 
-If you need to [include only containers with the enable label](https://containrrr.github.io/watchtower/arguments/#filter_by_enable_label), pass the `--label-enable` flag or the `WATCHTOWER_LABEL_ENABLE` environment variable on startup and set the _com.centurylinklabs.watchtower.enable_ label with a value of `true` for the containers you want to watch.
+=== "docker-compose"
 
-```docker
-LABEL com.centurylinklabs.watchtower.enable="true"
-```
+    ``` yaml
+    version: "3"
+    services:
+      someimage:
+        container_name: someimage
+        labels:
+          - "com.centurylinklabs.watchtower.enable=false"
+    ```
 
-Or, it can be specified as part of the `docker run` command line:
+If instead you want to [only include containers with the enable label](https://containrrr.github.io/watchtower/arguments/#filter_by_enable_label), pass the `--label-enable` flag or the `WATCHTOWER_LABEL_ENABLE` environment variable on startup for watchtower and set the _com.centurylinklabs.watchtower.enable_ label with a value of `true` on the containers you want to watch.
 
-```bash
-docker run -d --label=com.centurylinklabs.watchtower.enable=true someimage
-```
+=== "dockerfile"
+
+    ```docker
+    LABEL com.centurylinklabs.watchtower.enable="true"
+    ```
+=== "docker run"
+
+    ```bash
+    docker run -d --label=com.centurylinklabs.watchtower.enable=true someimage
+    ```
+
+=== "docker-compose"
+
+    ``` yaml
+    version: "3"
+    services:
+      someimage:
+        container_name: someimage
+        labels:
+          - "com.centurylinklabs.watchtower.enable=true"
+    ```
 
 If you wish to create a monitoring scope, you will need to [run multiple instances and set a scope for each of them](https://containrrr.github.io/watchtower/running-multiple-instances).