Where does my Pink toilet chemical go?

Toomanycars

As can be seen, we are new to carvanning and are preparing to go away for the first time next week.

I have run everything up in the van we've bought, just to make sure, but we are struggling to know where to put the Pink toilet chemical?

We know the Blue one goes in the waste tank itself (although when and quantities would be helpful).

Any help would be much appreciated as we wouldn't want our first conversation with a fellow caravanner to be toilet based!!

Our caravan is a Bailey Pegasus 546 if that makes any desceranable difference?

Thanks in advance