For an independent samples t-test, the general null hypothesis states that the mean of group one doesn't differ from group two.
1. How do I determine what hypotheses are being tested?
Well look at the variable the groups are being compared on. Pretend group 1 is Males and group 2 is Females and that you are comparing them on IQ Scores. The null hypothesis is that the two groups are equal in terms of IQ scores. The alternative hypothesis is that they are not equal.
2. How do I determine which hypotheses are supported?
If there is a significance difference you have support for your hypothesis. Look at the p value. Is it below 0.05?
3. How do I show evidence that the hypotheses are supported?