Hey Everyone! ^^ , My Name's DlinkS so let's start...

1- Go to Documents/My Games/ Terraria

Picture : http://prntscr.com/eowbj5

2- Open config file with a text editor , right click - open with - choose a text program

Picture(Spanish) : http://prntscr.com/eowc95

3- Change ''UseExperimentalFeatures'' : False to ''UseExperimentalFeatures'' : True

Picture : http://prntscr.com/eowcpr

4 - Enjoy Playing a seeded world :D