There are couple of thing you may have to take a look : -
1) Make sure to that domain you added in 1st screenshot is resolving on you machine (accessibile on Sitecore server).
2) Add the beacon script on external website.
3) 2nd screenshot says domaininvalid error, this happen when you have not added matching rule (where request domain is <<externalwebsitedomain>>) on the externalsite item located at /sitecore/system/Marketing Control Panel/FXM/<<externalwebsitedomain>> (from content tree) as shown below.
Once you address these, publish the fxm site to see the results.