I always manually partition when I'm installing Ubuntu to make sure I know exactly what's going on. I recommend first shrinking your windows partition, generally labeled "OS C:" in Disk Management. Then start installing from your Live Media and follow this guide. Just skip "4. Free some space for Ubuntu" since you'll have already done that.

While in Disk Management you should be able to see a partition called "Recovery", "Restore", or "Lenovo". This is where Windows would be restored from.

The guide I linked to above is nice because it has screenshots. But here's a brief summary of what manually partitioning requires. Any specific questions please feel free to comment.

1. Shrink the Window partition using Disk Management inside Windows by however much space you want to give to Ubuntu and swap (absolute bare minimum I'd say is 15GB).


2. Boot your Live Media.


3. At step 4 about operating systems, click "Something Else".


4. Create a new swap partition in the free space. Making it the same size as your RAM is a good rule of thumb. But leave at least 10GB free for the next step.


5. Create a new ext4 partition in the rest of the free space and mount it at /.


6. Once the installation completes, if you can't boot into both follow this guide.