Choose "something else" when Ubuntu asks, during installation, about the installation target.
You will be able to choose directly to install Ubuntu system root partition (
/ mountpoint) to a partition on the SSD, and choose to install
/home on the regular HDD partition. You will be able to create, modify and format the partition in that part of the installation.
- Choose free space for the root partition on any drive (here /sda), and press "Add..." to choose size and mountpoint:
- Do the same for your HOME partition on your harddrive. Choose montpoint
Check that everything is alright (e.g. make sure the "format" option is unticked for your Windows partitions) and proceed with partitioning and installation of Ubuntu: