how do i restore text from previous back up

I assume you mean text messages. Here is how you restore from a backup:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Restore is an all or nothing process. You cannot selectively restore only messages, for example. And your device will be restored to the state it was in when the backup was made. In other words, everything between now and when the backup was made will be lost on your iPhone.