The CSV should have two (or three) columns. The first should be the name of the primer, and the second should be its sequence. The third is an optional notes column.
The CSV should have a header (it'll be stripped off, so if you don't include a header your first row won't be checked). The actual content of the header doesn't matter.
Sequences can include whitespace, and it doesn't matter if they're in mixed case (some capital, some lowercase). If there are any characters other than whitespace or A/C/T/G, though, the sequence will be considered invalid and the row will be skipped.
Empty rows in the CSV will be skipped.
Here's an example of a well-formatted CSV file:
|ABC123||AAAAG cccggtgtgaacat||This isn't a real sequence.|
|DEF456||actgtGATtgtac||Neither is this.|
|GHI789||gattaca||Pretty solid film.|