You can assign employees to your different Managers (managers who have logins) so that manager can automatically access their team's results in their own login.
Give managers access to future surveys
This video explains how to assign employees to your managers. Once done, the results from any future surveys their team takes part in will be available in their Manager login.
Give managers access to previous survey results/open surveys
If you are looking to give managers access to a survey that you've already completed, or are still running, you'll still need to assign employees to each manager as shown above, and then once done go to the Status page of your survey and hit Resync. This will update all of the details in the survey to match your current People table, including giving managers who are now assigned to the employees access to the results.
IMPORTANT - Do not Resync to historic surveys as this will skew your data due to people changes you have most likely made since these older surveys e.g. people may have left since, or changed teams.