The tutorial by bnsfsubdivision / searchlights simulations is the most current, and best one in my opinion. Without ReDem, TS2015 can only handle 1 arc/second files (one .hgt file for each lat/long grid square). The first tutorial covers this process, and it is quite quick and easy. The second tutorial is meant for use with ReDem, and ArcGIS, or QGIS. This is a little more complicated, but will allow you to use 1/3 or 1/9 arc/second DEM. Both tutorials are oriented around the current USGS national map viewer site.
I couldn't find links to his original uploads of the tutorials, so I uploaded them to my dropbox.
1 arc/second tutorial (easy)
https://www.dropbox.com/s/xmbmqhsucgxe7 ... s.pdf?dl=01/3 or 1/9 arc second for use with ReDem and a GIS program
https://www.dropbox.com/s/xmbmqhsucgxe7 ... s.pdf?dl=0I used the second tutorial with ReDem and QGIS to create my Siskiyou route. I used the data from the USGS site, and was quite pleased with it.