Critical Value (T-Statistic Question)

Hey everyone,

I have gathered some data for a school project and I am calculating the various ways to express the data. I have come to the point where I should represent the t-statistics, but I am having some trouble with the critical value portion. I have already done the one sample t-test, and I have also calculated the degrees of freedom, and decided to use a significance level of alpha = 0.05, the problem is should I be taking the value from the t-table for one tailed or two tailed? My null hypothesis was Ho: mu ≤ 8 (which was my population mean for the one sample t-test formula), and my alternative was Ha: mu > 8. Also, depending on the which one I should use, how do I find out if I should reject my null hypothesis or not?

Thank you!