Apple ID Change

Follow the instructions provided earlier, namely: What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

She can then: Set up your iPhone or iPad - Apple Support

To answer your second question:

jsr03 wrote:

need to change user id ... and applications what do I do

Apps are permanently tied to the Apple ID that was used to download them. You wife will either need to download them with her ID (and possibly have to pay for ones that cost money), or you can set up Family Sharing which allows most apps to be downloaded for free if another family member (in this case you) has already purchased them.

To learn how to set up Family Sharing, read this support article --> Set up Family Sharing - Apple Support

You have to read -> this Apple article: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch -> What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

Then you have to remove the iPad from your account, see this Apple article:

Check your Apple ID device list to see where you're signed in

Check your Apple ID device list to find where you're signed in - Apple Support

Then your wife can sign in with her own Apple ID.