FInally solved, thanks everyone, this is the procedure i followed
for making screenshots, logo work these are the steps :-
1)for icons , feature graphics :-
location —> projectrootlocation(prl)/repo/(packagename)/en-US/icon.png and featureGraphic.png
2)Screenshots :-
location —> projectrootlocation(prl)/repo/(packagename)/en-US/phoneScreenshots/Screenshot1.png
- title, summary, text
location —> projectrootlocation(prl)/metadata/(packagename)/en-US/full_description.txt,short_description.txt,title.txt
but changelogs still not working
changelog location- projectrootlocation(prl)/metadata/package/en-US/changelogs/131.txt