So in order to understand the purpose of obfuscation and logging bypass you need to understand the workings of powershell logging. I could do a bit here but you're better off reading a more detailed run through so I've included a decent primer on the logging functionality below.
Once you have some grasp on logging you can follow that up with this article to actually see how you can bypass suspicious script block logging.
Bypass for PowerShell ScriptBlock Warning Logging of Suspicious Commands.
I should also point out that powershell v2, which is the default on Windows 7, provides very little logging and doesn't have suspicious script block logging so it is also possible to attempt to downgrade powershell to use the v2 engine as it does not offer the same logging abilities. Here is another article introducing the topic.
PowerShell Security: PowerShell Downgrade Attacks
I know I'm basically just providing other resources and not elaborating very much, it's just easier to point you somewhere else then try to cram it all here. Hopefully these resources can at least point you in the right direction.