new to Tasker
The beginner videos at menu / info / guides is the best place to start to get a good feel for the UI and tasker basics.
> Quick question, want to make sure WiFi
A WIFI connected context.
access a web site, enter a username and password
HTTP post action
and press Login button,
This will require root with a shell action 'input tap x y' or use the 'Auto input' plug in that does not require root.