system.xml

<?xml version="1.0"?>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../Backend/etc/system_file.xsd">
    <system>
        <tab id="bdc" translate="label" sortOrder="1">
            <label>BDC</label>
        </tab>
        <section id="simplenews" translate="label" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
            <label>Simple News</label>
            <tab>bdc</tab>
            <resource>BDC_SimpleNews::system_config</resource>
            <group id="general" translate="label" type="text" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
                <label>General Settings</label>
                <field id="enable_in_frontend" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Enable in frontend</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                </field>
                <field id="head_title" translate="label comment" type="text" sortOrder="2" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Head title</label>
                    <comment>Fill head title of news list page at here</comment>
                    <validate>required-entry</validate>
                </field>
                <field id="lastest_news_block_position" translate="label" type="select" sortOrder="3" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Lastest news block position</label>
                    <source_model>BDC\SimpleNews\Model\System\Config\LastestNews\Position</source_model>
                </field>
            </group>
        </section>
    </system>
</config>