Hi Andread333,
Thanks for your post! We understand that you are now in possession of an iPhone that has a passcode that you do not know. You will need to restore the device, which will erase the device. After the restore is complete, the device may come to a screen asking for an Apple ID and password, which you would need to enter before being able to add your own Apple ID. For steps on how to restore your device, and assistance with activation lock, refer to the support articles below.
If you forgot the passcode on your iPhone, or your iPhone is disabled
Activation Lock for iPhone, iPad, and iPod touch
Let us know what you find out!
Take care!