Not much rocket science required so i am gonna keep it short and simple.
Create a image in any online or offline photo editors, for example https://pixlr.com.
Create a blank image with no background. For Example:
Add the components needed for your app
Mandatory Component: Image Editor and obviously Canvas and Image Sprites.
Add the required images and the blank image which you previously made in Step 2.
Use the watermark effect block to set the following values to the “Blank Image”.
Image A: (The Blank Image)
Text: (The Text you want)
Text Size: (Use Trial and Error to find the right size according to the “Blank Image” Size)
Text Color: (According to your needs)
Text Underline :(According to your needs)
Text Alpha Value: (This is the Transparency of the Text) Use 255 for 100% visibility
Point X: (Again use Trial and Error to find the perfect value, also do not use 0 or less value as it will not be visible try to use half of the image width)
Point Y: (Again use Trial and Error to find the perfect value, also do not use 0 or less value as it will not be visible try to use half of the image height)
The Text can be used as a normal Image Sprite can be dragged and so on.
(Please suggest if the guide needs any changes as this is my first guide)