Most of the SWAT users use ArcSWAT, QSWAT or MWSWAT to create their models. The SWAT projects created with these tools could be opened directly in SWAT viewer. If you uses other tools, you could also manually create a SWAT project and open in SWAT viewer.
In this video, I will talk about how to open a SWAT project in SWAT Viewer. For your convenience, the time points for different tools was given below.
ArcSWAT 00:42
QSWAT 03:10
MWSWAT 06:30
Other Tools 09:20
Michael Yu 
Excellent job Michael,
Can you please also make videos on how to process waterbase soil and land use data?
Ameer
Hi Ameer,
Thanks for your comments. For the waterbase soil and land use data, do you mean the data download from water base website http://www.waterbase.org/download_data.html? Are there any difficulty to use that data? I want to know so the video could be more helpful.
Cheers,
Michael