You need to login with a user that has edit posts capacity?

Try this by keeping in current theme functions.php
Change your roles instead of author

function add_theme_caps() {
    // gets the author role
    $role = get_role( 'author' );

    // This only works, because it accesses the class instance.
    // would allow the author to edit others' posts for current theme only
    $role->add_cap( 'edit_posts' ); 
}
add_action( 'admin_init', 'add_theme_caps');