Hello Hassan, this is Emily.
So you want to be the child member and your dad is the organizer right?
First of all, you need to make sure you are in your dad's family group. On the computer, go to https://account.live.com, sign in with your dad's account, then go to Family. See if you are already added as a family member. If not, he needs to add you. Then you get the invite, and you can join.
After that, on his computer, make sure your dad has an account for himself using his own Microsoft account. And this user must be an admin user.
If you had previously added your account already on his computer, please while signing in as your dad's account, hold down Windows + R, type in netplwiz and press enter, then remove your account there first.
Restart the computer, sign in with your dad's account again. Go to Settings > Accounts > family, scroll down, you will find your email listed. Change the settings to allow sign in.
Restart the computer again, now you will see your account listed for log in. It should be all set from here. It is very important that you never change your Windows user on that computer into admin user. If you do that, none of the family safety feature will work.