I have been reading the comments on random posts and I found this being a common issue
How to jump in Terraria:
1) Create a character
2) Create a world
3) Type in google 'flip a coin' if it's heads, you need to do crimson, if it's tails then do corruption
4) Log in to your world with your created character

Step number 5 is very important so read closely

5) When logged in, press the spacebar on your keyboard (or if it's changed for some reason, the button that it's changed to) and you should perfom a big jump.

Hope this helps!