How to implement simple login functionality in WP?

Good day, there is a simple task
The website on WP, and button input. Registration will not be because the access is given manually, and will be only one accesses.
If the user has entered them correctly reloads the page and there is a unit ( + body issued a class)
When you exit( exit Button) Unit-concealed( even removed from hypertext markup language) And bodie removed the class
Please tell me how best to proceed in solving this problem
April 3rd 20 at 17:36
1 answer
April 3rd 20 at 17:38
Any plugin popup login form.

The body itself is the EAP specifies the class for logged in. Block... we don't know what the block, but 66% of issues at arm's length.
In General, plugins widgets with conditional logic, full - put this - to push there any block for logged -

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