Here is a rundown of all the different varieties of Infinitives using the 1st conjugation verb "porto" (look at the charts below to find more in-depth explanations of each type):

INFINITIVE FORMS:

	Active	Passive
Present	portare	portari
Perfect	portavisse	portatus esse
Future	portaturus esse	N/A

Present Active Infinitive: ("to _")

Use the 2nd Principle part of a verb
(e.g.: porto, portare, portavi, portatus -> portare = "to carry")

Present Passive Infinitive: (to be + "_ed")

Use the 2nd Principle part of a verb (see "Present Active Participle") and change the "e" at the end to "i" (Note: for 3rd conjugation verbs, chop off the whole "ere" and put in an "i")
(e.g.: portari = "to be carried")

Perfect Active Infinitive: (to have + "_ed")

Take the 3rd Principle part of a verb (or the Perfect Part with the "i" chopped off), and add "isse"
(e.g.: porto, portare, portavi, portatus -> portavisse = "to have carried"

Perfect Passive Infinitive: (to have been + "_ed")

Take the 4th Principle part of a verb, make the "us, a, um" 1st and 2nd Adjective endings agree in case, number, and gender with the subject, and add the word "esse"
(e.g.: porto, portare, portavi, portatus -> portatus esse = "to have been carried"

Future Active Infinitive: (about to + _)

Take the 4th Principle part of a verb, add a "ur" before placing the appropriate "us, a, um" ending (see Perfect Passive Infinitive) on the main part, then add the word "ésse"
(e.g.: portaturus esse = "about to carry")