Io tengo è scorretto in italiano. Viene usato al massimo nelle espressioni dialettali del sud italia. I Have è io ho.

Dear Bethany, just like Daniel said to you: I have - Io ho However, just like Andrew has just told you, you can't translate word by word literally cause it's not going to make any sense... To explain you further, look at this example: I am 27 years old, literally it would be - Io sono 27 anni (il verbo essere - the verb to be : io sono, tu sei, lui è, ....) But, Io HO un gatto - I have a cat (verb to have - avere: Io ho, tu hai, lui/lei ha, ...) I hope it was helpful to you.

io tengo

You should give some context! Word by word translation without context is not even done by computers anymore.