You can set text wrapping for your gallery using the following code using the HTML editor (this will not work using the Visual editor):
Replace "yourgalleryid" with your actual gallery ID. You may want to change the margins around the gallery by adjusting the values in the margin property. Currently they are 0 5px 5px 0 (top margin, right margin, bottom margin, left margin). You may also want to change the float property to right depending on your gallery placement.
Enter your text after the tag.
Here is an example: