How to insert a webitem in my jira pluigin page's sidebar

I create a jira plugin.There is a sidebar in my page,like this:
I want to add a webitem in red box.To click the webitem,a webpanel will show in the right page.

Now i success in project page,like this:

my atlassian-plugin.xml:

Now i have no idea about how to achieve it in my own plugin page,not only in project page.

Hello @11190

for Jira Server I put my web-item on section="admin_plugins_menu/my-section".
And it shows up under:

So maybe finding different sections fitting to your instance might help. It looks like you’re on Jira Cloud so I am not able to help further on that.