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What version of ANSYS are you using?
You need to acquire the S-N tabular data, either from an online source or perform your own fatigue testing.
Open Engineering Data, and in the Life category of the Toolbox, drag and drop an S-N Curve onto titanium alloy. Then copy and paste the data into the form. There is a Linear S-N Curve if all you know is the Fatigue Strength Exponent, m (slope) and Fatigue Strength Coefficient, A (intercept) and there is also a Bilinear S-N Curve.