Step 1: Set Up Windows Live Mesh
To get started, you'll need a Live Mesh account. You can get an account if you have a Windows Live ID, though it should be noted that Live Mesh is still in a sort of beta form called a Technical Preview.
Visit the Live Mesh web site to create an account.
Step 2: Create a Mesh Sync Folder for Your Windows Mobile Files
Once you have a Live Mesh account and you've installed the Live Mesh software on your PC, create a folder on your system in which you want to store files you can access from your Windows Mobile device. The folder can have any name and be located anywhere on your PC's hard drive. In this tutorial, we've created a folder on our Windows Desktop called "CAB Files" because we want to transfer .CAB software installation files to our device, but you can use any name or file type you'd like; create a folder called "Media" for image and music files, a folder called "Documents" for Word and Excel documents, etc., whatever suits your needs:

Once you've created the folder you wish to use on your Windows PC, right-click the file and select Add folder to your Live Mesh...:

You'll see a screen which confirms the request and finalizes the setup. When the folder is set to sync with Live Mesh, it will become blue:

By adding the folder to Live Mesh, a folder with the same name is created on the Live Mesh service; both the folder on your PC and the folder on Live Mesh mirror each other and sync to maintain the same contents. Changes to one folder will be reflected in the other, so if a file is added to the folder on our Windows PC, the file will be uploaded and stored in Live Mesh and vice versa. This mirroring feature is what allows us to transfer files to a Windows Mobile device using Live Mesh.
Our folder named "CAB Files" is now online and linked to our Live Mesh Desktop.
Step 3: Drag and Drop
So far we've created a Live Mesh Sync folder called CAB Files on our Windows Desktop. Now it's time to start moving files. Drag and drop the files you wish to copy to your Windows Mobile device into the Live Mesh Sync folder on your Windows PC:

After doing so (and allowing enough time to sync the files, seconds or minutes depending on your Internet connection), you'll see that the files you moved to the folder on your PC have been copied, or synced, with the folder of the same name on your Live Mesh Desktop:

Step 4: Access Live Mesh from Windows Mobile
Once the files have been synced with Live Mesh, you can access and download them within Windows Mobile.
Point your Windows Mobile web browser (Opera Mobile, Pocket IE, etc.) to http://m.mesh.com
and sign in.

Navigate to the folder you created (in the Folders tab), which in our case is CAB Files. Here you will see a listing of the .CAB files we synced with Live Mesh:

Tap a file to download it. You can save the file anywhere on your handheld or even to a storage card by using the Save As feature.

Final Thoughts
The Live Mesh platform is still being refined and at present, this web-based method is the only way to reach your files from a Windows Mobile device. Live Mesh will soon support Windows Mobile handhelds, which will make this process even more streamlined.
As you can see from our tutorial, you can use this method to move .CAB files to your Windows Mobile device for installation. It's actually quite handy to have a library of installation files online so that you can easily reach all of your Windows Mobile software for installation.
That "storage" aspect of this Live Mesh transfer method is why it's so impressive. You can easily drag-and-drop any file you wish to be available on Live Mesh to the Live Mesh folder or folders on your PC. You don't have to worry about FTP clients or premium service download sites. You can also share existing folders (My Documents, for example) and have each of those files available on your Windows Mobile device, with changes updated in real time.