Issues with unallocated partitions

I went ahead and split one of my partitions into two separate sections using EaseUS partition master, but once the process finished, I was left staring at this new partition labeled unallocated. When I right-click on it and select create partition, I get hit with this error message: "Please convert an existed primary partition to logical partition, and try again.". I click OK, but then... nothing. Just total silence from the computer.
I am quite stumped—how exactly am I supposed to perform this conversion? It’s all very confusing to me.
Does anyone have any advice on what my next move should be?

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"Hey, you'll need to switch that existing primary partition over to a logical one before you can move forward."

...Basically, what's happening is you're trying to squeeze another primary partition onto the same hard drive... but since you need a "logical partition" to make room, you've gotta flip that first one into a "logical p." instead.
...Bottom line is, you can only have one primary partition sitting there at a time.

The standard approach is to have one primary partition, typically your C: drive,
while all others should be set up as Logical partitions... like D:, E:, or F:.

Sometimes, a tiny bit of unallocated space ends up between the primary and logical partitions. It’s small, stays invisible in Windows, and won't cause any issues.
Since it's there, you can't actually turn it into a usable partition.
If that unallocated gap is under 1GB, why bother? Just leave it alone.

Multiple primary partitions are only necessary if you plan on installing different versions of Windows—say, Windows XP followed by Windows 7 as an add-on. But that requires covering the first one while creating the second. That's a completely different conversation.