You need to do a manual installation, the last option in the installation
screen. You need to do two things. You need to specify a file format and a
mount point. You will also do this on subsequent re-installations. You will
format both the first time but only format the root partition afterwards.
That way you can re-use home and preserve data and settings.

Use the smaller partition for root. Choose ext4 as the file format and check
it to format. The mount point will be /. Use the larger partition as home.
Use ext 4 as the file format and the mount point will be /home. It will
create user space in home later on in the installation. It can be on
separate partitions or drives. You will also want a swap partition depending
on the amount of RAM. It should not exceed your RAM. You designate it as
swap space and it will take care of format. You will want only one swap
partition on your computer no matter how many Linux installations you have
or it will use all and slow you down.

If you need to partition first then you can use the Live CD to do it. I
prefer to do it ahead of time, but there is no reason not to do it at the
time of installation.I also like to do each thing separately. I would shrink
one partition and Apply before I do the next step. That way if there is a
problem you can fix it easier. It is sometimes difficult to keep track of
the number of zeros, etc. and create a 35 MB instead of 35 GB partition.
Windows likes to be first, so if you have it put your Linux partitions
after.