Thank you, @jayna.
Every photo edit application has the option to add watermark. I use Photoshop Express (every photo requires some enhancements even if it looks good at first glance) and Watermark app for adding my signature. I like this one because it has many options to customise your watermark.
Looking forward to see your photos. Remember one thing: it doesn't matter the gear as long as your photos send a message. 🙂