The following tags 
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
of uses-permission has to stay out of tag application!
Edit
Try to keep it that way AndroidManifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.arielacrippa.saudetotal">
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
  <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
  <application
     android:allowBackup="true"
     android:icon="@mipmap/ic_launcher"
     android:label="@string/app_name"
     android:supportsRtl="true"
     android:theme="@style/AppTheme" >
  <activity
    android:name=".MainActivity"
    android:label="@string/app_name"
    android:theme="@style/AppTheme.NoActionBar">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
  </activity>
  <activity
    android:name=".Cadastros" android:screenOrientation="portrait" />
  <activity android:name=".Configuracoes" android:screenOrientation="portrait" />
  <activity android:name=".Relatorios" android:screenOrientation="portrait" />
  <activity android:name=".Usuários" android:screenOrientation="portrait" />
  </application>
</manifest>
							
							
						 
You can post the entire code of
AndroidManifest?– Igor Mello
Sure, follow the code:
– Ariela Crippa