the url is the AGOL or portal is the site used to setup to get the AppID.
This ID is then used to run the dev editoon. Check out the instructions I have in
anothe he great resource for understanding how to install and use widgets us Installing Robert’s Enhanced Search Widget for the Web AppBuilder
and then check out the Web AppBuilder Developer Edition - Customization Resource List for a list of resources for the dev environment.
Oh, it's mean that web App Builder is not free for use (because I have to buy license of Portal for ArcGIS and make AGOL account)...
Hmmm, can you tell me how to build Web GIS for free with ArcGIS (I just have ArcGIS desktop). Any plugin or other that can be used?
You can get a free AGOL account for development...of course it is limit
The free plan includes 50 credits per month so you can immediately start building powerful applications:
You need an AGOL or a Portal site, not both.
as Dan mentioned, the university may have something set up already, but if not, get a developer account so you can play and learn for yourself.