For Etsy sellers, since we don't have any way for a buyer to select gift wrapping directly, make sure you include gift wrap information in your listing along with instructions to add it in the note to seller or to send a convo. I also suggest putting that information in your shop policies and if you want your shop announcement as well. If you are using your own shopping cart and can add a checkbox or other direct way to request gift wrapping that would be the best way to do it.
For all handmade sellers online, make sure you are promoting your gift wrapping option on your blog/website and all your social media accounts. Offering gift wrapping can be a great selling point for your products but only if people know it's available.
For some other thoughts on packaging check out Making your Handmade Products Stand Out.