(New to FreePBX) Question about extensions

Sorry for this question, but recently my network guy quit the job and leave us with all the high tech and no explanation how to use it, i learn how to use FreePBX and learning more and more everyday.
I installed in my little company but not i come to a dilema that i didnt realize untill today, i have a maximun of 13 extension, how can i add more??? it may sound like a retarded question and i apologize for that, but i have no idea, i have search forums wikis and information and read that you can have lots and lots or extensions but i do not know how.

Please help or point me in the right direction.

many thanks.

Have you read the documentation in the wiki?

You didn’t tell us anything about the system so really no easy answer. You have to create an extension that matches the technology and settings of the phone you want to connect. Then depending on the version and how it was installed you have to push the configuration to the phone. Good installers automate this process, incompetent installers configure the phones manually.

Well so sorry, here is what i know…
i have in a pc running linux, with freepbx distro with asterick* , that we connect with two gateways one grandstream and the other dont remember, but totally 8 lines (analog) to the gateways and that to the pc running the programs.
i begin adding extensions but in the status page tell me 13 out of 13 extensions added, to be honnest i have not try to add more but i am afraid that if i add more i can do trouble you know.
hopefully that explanation is good, remember my understanding of the system is basic and i will answer all i can but not much, here i have seen really experts in the subjet.

thanks for your answer