You know, title is summarized, and the info is in the post, right?
Anyhow, perform block editing.
Block editing tutorial: https://projectpokemon.org/tutorials/save-editing/gen-8_157/block-editing-r106/
Where you can find the relevant blocks: https://projectpokemon.org/home/search/?q=Wild Area Event&type=downloads_file&nodes=203&updated_after=any&sortby=relevancy&search_and_or=and&search_in=titles
For wild area event #1 to #18, there's only 4 blocks to import.
Onwards, it's 5 blocks.
Make sure all the blocks are from the same event.
(also, for the record, if you share these online, they'll be updated with the latest event)
Info of "what block name" you need to import into:
https://projectpokemon.org/home/forums/topic/56121-swsh-blocks-and-save-research/
(the existing 4 blocks have similar key IDs, so easy to import. the Normal_encount_rigel1 is the one that currently doesn't have key ID up, but that thread will tell you where it goes.)