user-meta.php

<?php

// Add custom meta to user profile screen
add_action( 'show_user_profile', 'example_show_extra_profile_fields' );
add_action( 'edit_user_profile', 'example_show_extra_profile_fields' );

function example_show_extra_profile_fields( $user ) { ?>

  <h3>Payment information</h3>

  <table class="form-table">

		<tr>
			<th><label for="paypal">Paypal</label></th>

			<td>
				<input type="text" name="paypal" id="paypal" value="<?php echo esc_attr( get_the_author_meta( 'paypal', $user->ID ) ); ?>" class="regular-text" /><br />
				<span class="description">Please enter your Paypal email address for payments to be sent.</span>
			</td>
		</tr>

	</table>
<?php }

add_action( 'personal_options_update', 'example_save_extra_profile_fields' );
add_action( 'edit_user_profile_update', 'example_save_extra_profile_fields' );

function example_save_extra_profile_fields( $user_id ) {

	if ( !current_user_can( 'edit_user', $user_id ) )
		return false;

	/* Copy and paste this line for additional fields. Make sure to change 'paypal' to the field ID. */
	update_user_meta( $user_id, 'paypal', $_POST['paypal'] );
}