The Stress test for Dark Souls 3 is exclusive to PlayStation 4 and will run on these dates…:

Network Stress Test sessions
Friday, October 16th, 2015 at 8:00 p.m. to 11:00 p.m. CEST
Saturday, October 17th, 2015 at 8:00 p.m. to 11:00 p.m. CEST
Sunday, October 18th, 2015 at 8:00 p.m. to 11:00 p.m. CEST

You may register here.

The chance to get in the network stress test is apparently by lottery (chance), regardless on whether or not you have experience with the souls games.

The announcement for those who get in will be posted on these dates…:

Selection results announcement

Tuesday, October 13th, 2015 at 10:00 a.m. JST (planned)
Tuesday, October 13th, 2015 at 3:00 a.m. CEST (planned)
Tuesday, October 13th, 2015 at 1:00 a.m. GMT (planned)
Monday, October 12th, 2015 at 6:00 p.m. PDT (planned)

Once the selection lottery is complete, we will inform the winners via email.
You will not receive an email if you are not picked in the lottery.
Make sure to go to the Check Selection Results page on this site to check whether you were selected or not.
You can visit the Check Selection Results page on this site to see whether you were selected or not.
If selected, you can access the Check Selection Results page to obtain a product code that will let you download the Dark Souls III Network Stress Test version.

Good luck to those of you who want to get in to the stress test. Be sure to register!