Not sure about the last two questions, but for these two:
Quote by riza3: after a fresh install of both geeklog anfd forum plugin
how to show the link to forum so as new posts can be started to made
( by any user ) ?
how a registered user can add avtar ?
to change the menu read
here. you can also add a link in a normal block (admin menu / blocks / add new block)
to add an avatar, make sure that users can upload pictures in config.php. Then just click account info from the users menu and upload a picture. (make sure that the image directories are writeable and check the maximum image size in config.php.)