my 2008 ford ranger won't start. i replaced the battery and it just clicks when i try to start it

Have you checked your starter ?

i've had same issue check cables and / or connectors first . mine was the neg connection.

Make sure that all contacts on the starter solenoid are clean and tight. The solenoid can be found on the fender wall next to (or close by ) the battery. If every thing is good, I would replace the solenoid ( the part that is clicking ). You can also find it by following your red cable back to the fender wall. Remember that the solenoid must also have a good ground by mounting it firmly. As a rule of thumb on all Ford products, you will ware out 2 or 3 solenoids pr starter.

Did you check the alternator? Mine did the same thing, just clicked. Turned out to be the alternator.

Cheap first: Battery cables and connections, then usually auto zone or oreillys will check alternator and starter for free.