The import manager will open the dialogue to the right. Select the data to be imported and the export location. Click Ok. The next dialogue has information that needs to be provided (highlighted below). For the example dataset BIL and Signed 16 bit should be used. For more info on what signed/unsigned bits are look at the tables below snipped from ERDAS Hep file. Based on the charts below signed 16-bit is appropriate.
Also you need to determine the number of rows and columns for your data set using the following chart. http://www.ngdc.noaa.gov/mgg/topo/report/s11/s11C.html#table3
Now your .img file can be loaded into the ERDAS Viewer, but it doesn’t have spatial information. We need to set pixel size and origin of the image. Again, this data can be found in the NOAA Guide or viewed below.
The data is WGS 1984 Geographic lat/long. To add this information to the file.
You may have to close and reopen your image for changes to take affect. Do this to all of your globe images to prepare them for mosaicking. They should line up and match the etopo layer that you downloaded.
Your resulting image should look similar to below but of your chosen region