[Arkhelist]

Originally Posted by Coda

For -ru verbs, change the -ru to -rareru. For example, 食べる (taberu, to eat) becomes 食べられる (taberareru, to be able to eat).

It's considered slang, but for these types of verbs you may also encounter cases where the -rareru is just -reru　（食べる(taberu - to eat)→食べれる(tabereru - to be able to eat) 、帰る(kaeru - to return)→帰れる (kaereru -
to be able to return)
This case also functions as a -ru verb.

諦める(akirameru - to give up)→諦められない(akiramerarenai - to be unable to give up)→諦めれない(akiramerenai - to be unable to give up)

It should also be noted that you do not use the direct object particle を(wo/o) with the potential form. Instead, use は(ha/wa) or が(ga).
扉が開けた　(Tobira ga aketa - I/He/She/It was able to open the door/gate)
日本語が話せる (Nihongo ga hanaseru - I/He/She/It can speak Japanese)