A program available now that is free and you can boot off USB, is Gparted Live.
it may have more options than you need to try, but you could experiment with that.
Creating a partition is no risk.
Deleting a partition obviously deletes it. KIND OF HIGH RISK.(you might delete the wrong one) Make sure the partitions are labelled so you know which is which. There is a risk of deleting the wrong partition but you'd have to be a complete fool to do that. Make sure you check and double check before deleting a partition. If you have more than one hard drive in there, then remove/detach any hard drives with important data on them, before partitioning, just in case of a human error. Backing up beforehand ensures no risk. Many programs you boot off, don't show you the contents, but you can see the capacity and label. Even before I knew the software would show the label, I still managed to not make an error, because I checked the capacity of the drive. So I knew what drive or partitions on the drive, I was working on. I would check and double check. When you label the partition it is must more fool proof(after you've checked and double checked that you got the label right! and labelling a drive isn't technically part of partitioning or a function of partitioning. it's just a must to be safer). You can always backup beforehand though. I've never made that mistake of deleting the wrong one.
Changing which partition is bootable. This is KIND OF HIGH RISK. If you make the wrong partition bootable, you won't be able to boot, though this is always reversible.
One partition on a hard disk, has the bootable flag. The BIOS chooses which hard drive to boot from, and after that, the partition with the bootable flag is booted from.
I have probably made the wrong partition bootable before, because I didn't care about getting it wrong. I didn't need to waste effort and get stressed over doing it right 'cos it's reversible. And you can always experiment with it.
Resizing a partition - HIGH RISK. (though i've had no problem in 10 years). i've heard partitions can be corrupted by this. You could run chkdsk after to check. If there's a powercut during it then who knows what'd happen. You may want to backup if there's important data, before resizing, if you do it at all. But this is only high risk if it goes wrong. And when it goes wrong it's not really human error. Personally it has not gone wrong for me in a decade. I may have seen a partition was corrupt recently after, I don't know if it was from that, though chkdsk probably fixed it. It wasn't important stuff anyway. But if you resize and run chkdsk and it seems fine then it's fine. You can always backup beforehand as I said, and that tends to be recommended. If resizing did go wrong, it's a)not human error b)not reversible. The only smart thing you can do to avoid this, is backup. Or just do this with a partition that doesn't have important stuff on it.
What you need to know, and I say "need" in the sense that it's just fundamental to know. It's no risk if you don't know and you'd find out soon enough and in a gentle way. There's no risk if you didn't know the following. The "risks" are those I mentioned above. As for some basics about partitions.. You create a primary partition maybe more. Gparted Live won't let you create more than four.
If you want any more partitions, you have to create what is called an Extended partition which is like a container - Gparted says it's a primary so it counts it in one of its four. Then within the Extended partition you can create as many "Logical partitions" as you want.
The bootable partition might run a boot loader, in linux I suppose like GRUB, and if there are other partitions then the boot loader software can boot an OS of any of them, but this is not part of the partitioning process.
Gparted Live won't let you convert e.g. a Primary to a Logical. Many Windows programs let you and no doubt linux ones too. If there is risk here i've never run into it.
You can make a logical partition bootable. So i'm not sure of any advantage in multiple primary partitions, beyond a primary and (if more partitions are wanted) an extended.
By the way, many people use virtual machines as an alternative to partitioning.