Firstly, you'll need to go to Project Settings under the project you'd like to add mention to
Then, find Sources tab
You'll see Add mention manually over there
Once you click on Add mention form, you will see a field where you have to enter URL address of a mention you wish to add:
Click NEXT and this window will show up
Fill in the form and click Save to add a mention to the project. After that, they should appear in your results in your dashboard :)