Assuming your images have sequential file names (picture-001.tif, picture-002.tif, picture-003.tif, etc.), click File / Open. Browse to the directory containing the pictures and click on the first one. In the lower left corner of the Open dialog box is a checkbox for image sequence; check this. Click OK. All the images will be loaded into the timeline as if they were a single video clip. Right-mouse-button click on the clip and choose Properties, then click the Media tab. There is an entry that lets you set the frame rate.