Hello Ashirbad Kumar,
You can follow the below link it may useful.
I think for a newcomer having all the different portals is super un-intuative? also their naming conventions are all over the place.
the desktopmodeler is your main tool that you download.
mendix.com = saleswebsite
community.mendix.com = where the community can be found
sprintr.home.mendix.com = is the developerportal but most ppl just call it sprintr (to make things more confusing)
appstore.mendix.com = where you can download widgets (and not where your made apps are found)
I hope this helps you out a bit.