Here are the steps you should follow:

1. Get familiar with the material in [SQL Server Agent Fixed Database Roles][1].
2. Decide which one is good for you
3. Use a script similar to the following one (but first choose specific msdb role) to achieve what you ask for:

 USE [master]
 GO 
 CREATE LOGIN [DOMAIN\user] FROM WINDOWS 
 GO 
 USE [msdb]
 GO
 CREATE USER [DOMAIN\user] FOR LOGIN [DOMAIN\user] 
 GO
 USE [msdb]
 GO
 EXEC sp_addrolemember N'SQLAgentOperatorRole', N'DOMAIN\user'
 GO

 [1]: https://msdn.microsoft.com/en-us/library/ms188283.aspx