As previously announced, the first six episode season of the two season order will premiere this summer, and the second season will air in 2016 (see “’Walking Dead’ Spinoff Gets Two Season Order”).
It's unclear at this point what the associated merch will be like. Presumably there will be a licensing stream separate from The Walking Dead's, but whether or not the narrative will be developed in any ways other than the series (i.e., comics) is yet to be seen.