Here you need more of the context, which I found online, so:
Quo rex cum intervenisset et rogitaret, cur id faceret, illa ementita est dicitque eos sceleratos signum contaminasse; quod impii et scelerati homines in templum essent adducti, signum expiandum ad mare ferri oportere et iubere eum interdicere civibus, ne quis eorum extra urbem exiret.
Like Babelfish said there are only infinitives, but in context it's a continuation of the indirect discourse, so I would see it as something like:
[and she said that] because the impious and wicked men had be lead to the temple, the sign to be purified ought to be carried to the sea and he ought to order the citizens to forbid any of them from going out of the city.
For the last passage, the site I found punctuates it as Rex sacerdoti dicto audiens fuit; occasione Iphigenia nacta signo sublato cum fratre Oreste et Pylade in navem ascendit which makes it clearer, something like (being very literal):
The king obeyed the priest; Iphegenia, the chance having been obtained, the sign having been taken away, went up on to the ship with her brother Orestes and Pylades.
At first I thought "nacta" would go with "Iphigenia" and be nominative, but it seems to be ablative and go with "occasione." Looking it up in the dictionary, "nanciscor" seems to be one of those deponent verbs whose passive participle can be an actual passive.