This is only a quick guide, so sorry if I have missed anything out! Written very simply to try and avoid confusion (sorry if it is very long-winded!)
Mobile Atlas Creator part
Download Mobile Atlas Creator from:
http://sourceforge.net/projects/trekbuddyatlasc/]Mobile Atlas Creator link[/url]
Think you need to unzip it first, then go to wherever you have unzipped it to and click on the Mobile Atlas Creator icon.
You should get a screen similar to this:
but yours will be just showing a view of the world.
In the top left hand corner of the screen there is a list under the ‘Map Source’ button. It lists all the different open source maps available. For UK OS maps you want to select ‘Multimap UK OS Map’ from the dropdown list.
Next you want to scroll on the map to the area that you want to create a map for. To select an area left click and drag over an area. A red box will appear highlighting the area you are selecting. You select different scales (or zoom levels on your phone) by checking the boxes in the ‘Zoom Layer’ box. Lower numbers give you large areas at low resolution, higher numbers give the more detailed maps but obviously will increase the number of tiles downloaded, and therefore will be larger file sizes. Personally I use Zoom levels 14 and 15 which corresponds I think to 1:10000 and 1:25000 OS Maps. Layer 16 gives the same detail as 15 but zoomed in.
Leave the ‘Layersettings’ box as the default settings.
The ‘Atlas Content’ box is the name you will see the maps stored to. By default the name given to your atlas is ‘Unnamed Atlas’. Make it something recognisable (e.g. Sheffield). You can rename the atlas by pressing F2 or right clicking and selecting rename. The namebox is the name given to the individual layers (i.e. Sheffield 14, Sheffield 15), where the number correlates to the zoom layer (the numbers are added automatically, so for the above example I would put Sheffield in this box.
If you are happy with the area you have selected and the zoom levels, press the ‘Add Selection’ button and you will see your maps added to the atlas in the ‘Atlas Content’ box.
In the next box ‘Atlas Settings’, make sure TrekBuddy tared atlas is selected from the dropdown menu.
Finally press the ‘Create atlas’ button to create your maps. A dialog box will appear for a few seconds (longer for larger maps), and will tell you when completed successfully.
You now have your maps downloaded to your computer, now you need to send them to your phone and put them in the right folder.
Phone part
Connect your phone and mount as disk drive.
Open the Mobile Atlas folder on your PC. Look for the atlases folder which should be in the same place as the Mobile Atlas Creator launcher icon you used at the start. If you open the ‘atlases’ folder you should see your folder that contains the maps created a minute ago (e.g. Sheffield in my example).
In a new window on your PC find the folder on your phone for TrekBuddy stuff. It should be in your SD card folder, labelled ‘TrekBuddy.’ Go into this folder and you will find a ‘maps’ folder. Open this folder and copy across the maps folder you found for the step above.
The maps are now on your phone! Unmount your phone in the same way you would take out a USB stick, wait a few seconds for the phone to check the SD card and then open TrekBuddy. If you are wanting just one zoom layer you can use ‘Load Map’ from the menu and select just one of the zoom layers. Alternatively you can select ‘Load Atlas’ which will load all the zoom layers and allow you to quickly change between the zoom layers. You can do this by selecting your atlas and then selecting the file labelled ‘cr.tar’. If you can’t figure this out I can pull up some screenshots but think this post is already getting pretty long!
There are more options for customizing TrekBuddy such as using a CMS which gives a graphical output of your route in real time but this involves some more copying of files. For now the above will allow you to play around with TrekBuddy to see if you like it. There are other similar programs out there each with different views on what makes a good offline GPS program. Each has its advantages, discussed a few days ago:
Android GPS war
Let me know if you get stuck, but hopefully you shouldn’t! Again apologies if this is over-simplified but hopefully it will get you up and running! 
