Hi,
You have to configure on each PC an IPv6 address. Ex: PC1 FD00:1:1:1::2/64
If you want that your PC can ping each other, an IPv6 gateway will be to configure on each PC.
The gateway is the IPv6 adress of the router on the same subnet.
At this point, each PC can ping the its router (default gateway)
PC1 and PC2 can ping in both way because the router know the route to join the 2 subnet (route are directly connected because the router has an interface in each subnet)
it's the same thing for PC3 and PC4.
To finish, you have to configure IPv6 route on each router.
On R1, the route to join FD:1:1:3::/64 and FD:1:1:4::/64
On R2, the route to join FD:1:1:1::/64 and FD:1:1:2::/64
EDIT : Sorry, OSPF is correctly configured between the routers. So you don't need to configure ipv6 static route