What are the requirements?
Console players will now need a Battle.net account linked to their Xbox, PSN or Nintendo account. If you are a PC player you don't have to worry as you should already have this.
What are the limitations?
You will be able to play with anyone no matter what device they are using to play on as long as they have a Battle.net account. Competitive will be split between console and PC. If you have accounts on multiple systems cosmetics, stats, SR will not be transferred between them. PC matchmaking will work with PC only but console players grouping with PC will be put in PC matchmaking pool. PC can not join console matchmaking, aim assist on consoles will be automatically disabled when in PC pool, but remain available in console pool. Cross and competitive (console only) the cross play competitive season will remain separate until the start of Season 29 on the 1st of July.
Do bear in mind that cross play can be turned off and that every account will get a Golden Loot box for every format they play the game on. If you have any further questions on this change please do check out the official post HERE as it includes all we know as of right now.