This is a common question and has been answered numerous times in AskUbuntu (for example, here).
In short, you probably have
fast boot turned on in Windows, which is why Linux will only mount it in read-only mode.
You should also have
ntfs-3g installed, which you likely will because it is installed by default on Ubuntu
Q1. Just mount your Windows partition and see if you can create or edit a file there.
Q2. To mount it reliably in read-write mode, you need to disable
fast boot in Windows. Then just double click the Windows partition in your file manager. Alternatively, you can do it from the terminal:
Find out which partition is your windows partition:
[van@z97:mnt]$ lsblk -f
NAME FSTYPE LABEL UUID MOUNTPOINT
loop0 squashfs /snap/ohmygiraffe/3
loop1 squashfs /snap/core/2844
loop2 squashfs /snap/core/2774
loop3 squashfs /snap/core/2898
├─sda1 ntfs Recovery E6A60CE2A60CB559
├─sda2 vfat A80E-CD6E /boot/efi
├─sda4 ntfs 3C5E17DD5E178F30
├─sda5 swap e0f12aa3-2b9f-4e04-a91d-806a9eccb688
│ └─cryptswap1 swap c738647d-8719-4f4e-b454-14802635d295 [SWAP]
└─sda6 ext4 4295796e-0535-4fbf-843d-7c9970c9155e /
├─sdb1 ext4 4c9ee94a-d2b3-46a0-99a7-7f434814bda5 /home
└─sdb2 ext4 cc902d7c-591b-4a44-8b68-51a7ca7c4e7f /opt
In my example above, it's
Now mount it to mount-point
sudo mount -t ntfs /dev/sda4 /mnt/windows
Then just navigate to
/mnt/windows in your file manager and create a test text file and make sure you can save it.
You can umount the mount using:
sudo umount /mnt/windows