Step 1 : Enable the trigger module if you haven’t done so. (To enable the trigger module, go to administer->site building->module. check the trigger module and press save.)
Step 2 : Go the administration panel and click on action. Under Make a new advanced action available, select Redirect to URL… and hit create.
Enter a description and the url to redirect to. You can use internal url like node/123 to redirect the user on login.
Press Save.
Step 3 : Go to the administration panel and click on triggers under site building. Select users in the tab.
Under Trigger: After a user has logged in, select the trigger you have just created and hit assign.
Logout and log back in to test.
Thanks!!