In order to allow connect to Mikrotik Router WebFig remotely, you should add a firewall filter and NAT rule for remote connection in WebFig.

1) Create a firewall filter

The first action you should do is to add filtering option for port 80 at IP → Firewall → Filter Rules → Add New

And then you should make sure if you put following item correctly

You may able to locate above filtering information after #6 like below:

2) Creating a NAT rule by IP → Firewall → NAT → Add New

And you should check followings

Note that you can change the connection port number if you want

Now you can connect to WebFig remotely.