Could you please share a bit more about your scenario?
Do you want to send an attachment to a SP list item using PowerApps?
If you want to send an attachment to a SP list item using PowerApps, I think this feature has been achieved within PowerApps already. More details about uploading attachments to SP list, please check the following blog for more details:
So we are trying to have this capability on a free standing app that we've built on PowerApps. Not within Sharepoint itself. Specifically we are trying to get powerapps to send an image (.jpg) to a sharepoint list using this app we've built.
This is not the option we are looking for:
But rather, we are looking for a solution in this: