Ensure that your file has been downloaded and unzipped to use.
1- Open AI.

2- Open the image/project you would like the texture on.

3- If you have a design with more than one object that you would like the texture on, select them all and group them together.

4- On the top toolbar, select Window. A drop-down box will appear. Scroll down and select Transparency. The Transparency panel will appear in your workspace.

5- Select the three little lines in the Transparencypanel(on the right and highlighted by the red arrow in the pic). A drop-down box will appear. Select Show Thumbnails. This will expand the Transparency panel.

6- Double-click on the grey square to the right of the thumbnail of your image in the Transparency panel (1). This will create an opacity mask. Your image may disappear since your mask begins as a black box to indicate it is opaque. Don’t worry this will change when we add the texture.
Click on File > Place in the top toolbar (2) to select your texture.

7-The Placewindow will open. Select the texture you would like and click Place.

8- Your texture will now appear over your image.

9- Resize the texture to cover your image.

10- Double-click on the image thumbnail in the Transparency panel to continue working on the image and not on the texture mask.

During this tutorial we used a watercolor texture background from Design Bundles.