The tie-rod and nut may just spin freely as you're trying to thread a tie-rod end onto it. The inner end of the tie rod is a low-friction ball joint at the steering rack, and there's nothing there that can resist rotation. So, you just need to grip the tie rod with something to prevent it from rotating as you're threading on the tie-rod end (I use a pair of pliers with tape on the jaws to prevent marring of the rod).