How to add and save avatar on registration and profile page?

Hi! I’d like to add user avatar on registration and profile page.
Here’s how I create the fild, but I don’t know how can I save it in data base. Could you help me?

<h3>Upload avatar</h3>
        <?php echo get_simple_local_avatar( $profileuser->ID ); ?>
        <?php
          if ( ! $upload_rights = current_user_can('upload_files') )
            $upload_rights = empty( $this->options['caps'] );

          if ( $upload_rights ) {
            do_action( 'simple_local_avatar_notices' );
            wp_nonce_field( 'simple_local_avatar_nonce', '_simple_local_avatar_nonce', false );
        ?>

        <p>
          <input type="file" name="simple-local-avatar" id="upload_hidden" onchange="document.getElementById('upload_visible').value = this.value;" />
          <button type="button" id="review" onclick="document.getElementById('upload_hidden').click();">Выбрать</button>
        </p>

            <p>
              <?php if ( current_user_can( 'upload_files' ) && did_action( 'wp_enqueue_media' ) ) : ?><a href="#" class="button hide-if-no-js" id="simple-local-avatar-media"><?php _e( 'Choose from Media Library', 'simple-local-avatars' ); ?></a> ?<?php endif; ?>

            </p>
        <?php
          } else {
            if ( empty( $profileuser->simple_local_avatar ) )
              echo '<span class="description">' . __('No local avatar is set. Set up your avatar at Gravatar.com.','simple-local-avatars') . '</span>';
            else
              echo '<span class="description">' . __('You do not have media management permissions. To change your local avatar, contact the blog administrator.','simple-local-avatars') . '</span>';
          }
        ?>

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