Will this delete the old content the SD Card had? And also, is there a tutorial for this that I can go through?You absolutely can.
Instead of doing directly in Hekate, take your SD card out and plug it into a PC with a partitioning software such as Gparted installed.
You can now manually downsize your partition and create a new ones for Android.
You'll need to create several partitions with specific sizes and names.
See the switchroot wiki for more details.
https://wiki.switchroot.org/wiki/documentation/partition-docs