adds docs for lightdash upload and download selectors to guide doc

docs/references/content-as-code.mdx

@@ -66,6 +66,34 @@ lightdash download -c https://app.lightdash.cloud/the-url-to-my-first-saved-char
 
 From the [Lightdash CLI](/references/lightdash-cli), you can use the command `lightdash upload` to upload any changes you've made to your charts or dashboards as code. To upload new charts that you've created as code to your Lightdash project, you need to run `lightdash upload --force`
 
+### Use `lightdash upload -c` or `lightdash upload --charts` to select specific charts
+
+For example, if I only wanted to upload a specific saved chart as code, I would run the command:
+
+```bash
+lightdash upload -c my-saved-chart-slug
+```
+
+You must specify the chart using the chart's SLUG. 
+
+### Use `lightdash upload -d` or `lightdash upload --dashboards` to select specific dashboards
+
+For example, if I only wanted to upload a specific dashboard as code, I would run the command:
+
+```bash
+lightdash upload -d my-dashboard-slug
+```
+
+You must specify the dashboard using the dashboard's SLUG.
+
+#### To select multiple charts or dashboards, add a space between the items
+
+For example, this command would select two charts to upload:
+
+```bash
+lightdash upload -c my-saved-chart-1-slug my-saved-chart-2-slug
+```
+
 #### Only content as code that you've made changes to will be uploaded 
 
 For example: