If your file format is not one of the supported input there is no need to worry. Getting your files into the right place is relatively easy. The easiest way to do this is by using Iris itself. Sections and slices can be created through Iris, and images can be dragged into their appropriate locations.
If you have a large amount of data and are thinking about writing a script, below shows how Iris stores it's data.
A number of slices make up a section. In some data sets each section is also slice, in this case it may be easier to set up your data as follows.
Note: If you create this structure by hand Iris can import it. Just create a New volume in the root of the above structure. Iris will notice the structure and prompt you to import it. If all is in order with your structure it will import it without problems.
A .mosaic file is simply a file that explains the positions and transforms of each image in the mosaic. This lightweight file prevents storing out large amounts of data and keeps your original files intact.
If your file format is not one of the supported input formats it will save a lot of time if you can generate a .mosaic file and place it in the Slice directory. This does require a rough knowledge about tile positions, but most microscopes provide this information one format or another.