Android Question permissions

I have an error as follows
(Exception) java.lang.Exception: java.io.FileNotFoundException: /storage/emulated/0/IoTLOG8Series/Buffer/C0000001.tmp: open failed: EACCES (Permission denied)
I know this is a question of permissions.
How can I join the permission?
Like this
maiifest edit:
....
AddPermission(android.permission.MANAGE_DOCUMENTS)
AddPermission(android.permission.WRITE_EXTERNAL_STORAGE)
AddPermission(android.permission.READ_EXTERNAL_STORAGE)
AddManifestText
(
<uses-permission
android:name="android.permission.WRITE_EXTERNAL_STORAGE"
android:maxSdkVersion="18" />
)