Text

<?php

$tea_content = array(
    array(
        'type' => 'text',
        'title' => 'What do you like?',
        'id' => 'my_text_field_id',
        'default' => "Penguins, I am sure they're gonna dominate the World!",
        'placeholder' => "McDonald's as well",
        'description' => 'Put in here everything you want.',
        'maxlength' => 120,
    ),
);

Or if you need to add some details...

<?php

$tea_content = array(
    array(
        'type' => 'text',
        'title' => 'How much do you like Penguins?',
        'id' => 'my_text_field_id',
        'default' => 100,
        'placeholder' => '50',
        'description' => 'Tell us how much do like Penguins to have a chance to get into our private Penguins community ;)',
        'options' => array(
            'type' => 'number',
            'min' => 10,
            'max' => 100,
            'step' => 1,
        ),
    ),
);

Retrieve data

Using the _get_option('my_text_field_id') method, you'll get (with a json_encode() display):

"Penguins, I am sure they're gonna dominate the World!"