trying to build a sample from the sp-dev-fx-extensions gitub repo (react-application-announcements)

I am fairly new to SharePoint, so bear with me as to what I am doing wrong to implement this program.

Here's what I've done:
1. npm install
2. gulp serve - that opened a browser where the url was a localhost: "https://localhost:4321/temp/workbench.html"
3. I opened another tab, typed in our sharepoint url: "https://gosusd.sharepoint.com/sites/ITHub"
4. I appended the following query string to the end of the sharepoint url:
“?loadSPFX=true&debugManifestsFile=https://localhost:4321/temp/manifests.js&customActions={"dd7ec4fd-97aa-44c5-b6ad-87535862e0bf":{"location":"ClientSideExtension.ApplicationCustomizer","properties":{"AnnouncementList":"Annoncements","siteUrl": "/sites/ITHub"}}}"
5. no resulting banner on the site, I've changed "siteUrl" to the sharepoint site, I've then put in the complete sharepoint url after "siteUrl", I'm not sure how to troubleshoot, would someone give me some guidance on what I've done wrong here