Simply use the left panel for the text you actually want it to say and then as you do this, you should see in the following panel that you have some pretty wacky things going on with the text. As you can see, it turns super glitchy. However, you are actually able to copy and paste this into wherever you want to use it that will accept the Zalgo text font.
T̵̡̧̨̖̪̗̠͔̰̓̈́̕͜ẖ̷̙̪̮̭̖̮̯̘͋͐̃̅͌̈́̆̕ͅȉ̶̛̫̟͎͋͗̓s̵̡͔̻͆̄͘ i̴̟͔͚͔͗͠ś̴̳̗͙ a̵̧̳͇̜̪̣̅̓n̸̛̰̼͇̱͐̎̀̽̌̐̿̈́̓ͅ ḛ̴̟̉͗x̷̬̩̀̕à̵̡̭̫̤̯͇̫͓̘͊̑͐̎̍͠m̶͎̦̾̾͠p̷̗̬̯̰͙̣̮̋̈́͆͊̇̿̋l̸̨̘̞̗̩̞̱͖̏̍̽̆͜͜e̸̱̹̬̞̹̍̇̓ͅ o̷̊ͅḟ̴͈̆̔̾̒́ g̴̤̪̻̰̗̀̓̎͋͝l̷̨͇͔͈̤̝̊̀̂͛͜į̴̡̦̼̄̏̏͛̒ẗ̶̙̻̜̺͉́̽̒̅̀̐͝c̸̛̛͇̱͇̮͔͔͙̼̀̈́̀͜h̵̙̘̣̻͈̫͇̜͂́̍͊͗̀͜ t̷̬̹̜̼̫̘͒̊ę̷̰̬̠̭̠͉̳̐́̒͑͋̓̎̽̈́͠x̷̢̢̛͓̜͚̖̜͕̼̙̌̍ţ̵̖͖̜̜̪́̎͒̚͜͝.̷̛̬̖̳̻̪̩̾̾̆̄̓͋͒̚͠