Locations:

1. Content -> Content by Section -> Newsflashes  (Adsense channel: MainMenuSmallRectTop)

2. Modules -> Site Modules -> New Module  (Adsense channel: MainMenuWideSkyLeftBottom)

3. Content -> Frontpage Manager -> Article  (Adsense channel: ArticleHalfBannerTop)

Is there a way to just insert adsense directly into content without modules?

How about a plugin?
AdSense Plugin

AdSense Mambot

Usage : {mosgoogle} in content or AutoAds “ON” displays a Google Ad as specified in paramenters.

You can also use {mosgoogle left}, {mosgoogle right}, {mosgoogle none} and {mosgoogle center} if you want the ad align differently from the set parameters.
Add a channel id after the align param or only channel id to select individual channels for your ads

You can choose to display Ads or AdLinks, Collapse empty ads or replace them with an alternate ad or color

2.0
Added some new features like AutoAds, Alternate Ads and Colors, and collapsing.
2.1
Added {mospagebreak} support for AutoAds and AutoAds position (top/bottom).
2.2
Added multiple exclude sections. Added parameter to hide ads in Intro only view.
New parameter “channel” : Use {mosgoogle align channel} to select a channel to use from the content editor.
Channel info can also be fetched from com_user_extended: channel info will be taken from the authors user information, defaults to field user15

Please report any bugs to Christian, thanks.

For more information, visit MamboSphere.com

it is simple to add adsense to content. Turn off rich text editor in joomla global configuration (Choose No WYSIWYG Editor) and directly post google code inside your content and it will be published as it is. no need of any module or anything to post…(remember to override the write-protect when saving the new configuration)