Please, first have a look on the existing thread about this question:related discussion: To Freeze - how to say in German
You may more easily distinguish the German words with the following short explanations
frieren = to be cold (occ. = "gefrieren")*
gefrieren = to freeze (what happens to things)*
einfrieren = to freeze + an object(= a person doing it to an object, normally using a freezer)
* F.i. Der See gefror über Nacht. (occ. Der See fror über Nacht.) past tense
Only "einfrieren" is a transitive verb (as it demands an object).
Regularly there are no reflexive forms. But you may hear "mich/dich/etc. friert (es)" which is used regionally for "ich friere/du frierst/er-sie-es friert/etc."
The sentence "Ich friere mich ein" - if at all - could only be imagined in cryonics ;-)
The perfect tense uses the auxiliary sein
only for "gefrieren", so "frieren" and "einfrieren" are formed with haben
. So you can distinguish the meaning of
"er hat gefroren" - he froze (= had cold)
"er ist gefroren" - it (let's say the lake) is frozen