Even though Seesaw is not designed for sharing resources, there are two ways to repurpose it to do this...
Create a post that contains a resource, don't tag any people in it, just add a folder to the post, this will make it easy for students to find, when they click on 'Class Feed' in Seesaw. You could also create a folder with your name, so kids know to click on .Mr McHugh to find any resources you've posted.
However... this has two problems:
It’s a little buried, so kids have to look for it, by clicking on the Class Feed folder, then they find and click on the resource folder.
If kids make a copy of this resource using Copy & Edit, it automatically gets assigned to the same folder…
I've already created fake students like '.Writing' that you can add to any class. In Manage Class, add search for the name, eg 'Writing' Seesaw should search and locate the student, then you can add them to your class.
Now you can use this 'student' post resources to that 'student'—students will easily be able allocated any resources you've posted by clicking on your name, and they'll be able to identify the type of resource by seeing the folders you have labelled the resource with.
This has two advantages:
I've created students in the Seesaw that you can add to any class, just type in the subject, and it will appear. If the subject you want does not appear, let me know and I'll add it for you.