There should be a positive battery cable to the starter relay(often called solenoid), its mounted on the inner fender, has 2 larger posts and 1 or 2 smaller posts
FIRST remove battery negative cable!!!!!
Then remove battery positive cable from the Relay/Solenoids larger post, there WILL BE several other wires with it, those wires power the dash and all the other electrics in the vehicle
So this is a very important post/connection
Clean it and all the wire ends, and put them all back on, and secure the nut
Now clean the battery negative cable end, its post should be clean if its a new battery, its a lead connector so soft metal, scrape it clean on the inside if needs be
Connect it to battery and tighten it
Remove battery positive from battery and clean it, put it back on and tighten it
Battery cables MUST BE tightened to work