A function template (*.rft.xml) is a saved raster function chain. If you want to apply a function template to a raster layer, perform that task using the Apply Function Template 
button, from the Image Analysis window.
- In the Image Analysis window, highlight the raster layer on which to apply a function template.
- Click the Apply Function Template button.
- Navigate and choose the appropriate function template file (*.rft.xml), and click Open.
Related topics
- Populating functions with values from the attribute table
- Accessing the Raster Function Template Editor
- Editing function chain templates
- Edit Raster Function
- Saving a raster function template from the layer's symbology
- Adding a processing template to a mosaic dataset
- Adding raster data to a mosaic dataset using a custom template