Installing Kali on an encrypted partition (dual boot with Arch)

I would install Kali on an encrypted partition, you help me?
I have a HDD of 500 GB and 250 GB are dedicated to ArchLinux (so I have several partitions such as boot, root, home, etc. etc.).
I inserted the DVD of Kali and I continued with graphical installation.
at the time of partition, there are several options including: Use entire disk for encrypted LVM ... but I do not want to use whole disk so I continue with Manual.
Now, if I take 115 GB (which is the space I want to dedicate to Kali) in Free Space and create a partition to use as "physical volume for encryption."
Then I go to the <Configuration encrypted volumes> but here I can only create another encrypted partition. so I decide to press ends and go and I have these errors:
SWAP, there must be a SWAP encrypted (how ????) and the mount point / (but if I press the physical volume for the partition I can not use it as /).
I should create another partition / and go but who tells me that then uses for / home etc. etc. the crypted partition (and not that of ARCH) with Passphrase but it don't give option to set passphrase (or I don't know how to do it) ..
it is convenient for the case encrypt the partition after installing Kali?