Log-in as service account in SQL Server Management Studio
Question is, can I login using a service account in SQL Server
  Management Studio?


How To Add A Service Account To Microsoft SQL Server


Open SQL Management Studio using SQL Authentication SysAdmin (SA)
Account.
Open up Security then Right Click on Logins, choose “New Login”
On the new login screen choose “Search”
On the search screen ensure you are searching the Entire Directory,
type in the user name, choose Check Names, then choose ok.
After you click OK, Click Server Roles and check “sysadmin”
Click OK and you are done
Test out by logging into SQL Management studio using Windows
Authentication.


For further your ref here and here