To shorten links in dlvr.it using bit.ly (or bit.ly pro) you'll first need a bit.ly account. If you choose to use a shortener other than dlvr.it's shortening service, dlvr.it will not track/report click stats for items. Stats will be found in the account of your new shortener.
1) Log in to your dlvr.it account and click the Socials tab.
2) Click Short Links.
3) Click +Add shortener
4) Choose bit.ly from the list of options
5) Click on Connect.
6) Sign in to your bit.ly account and click Continue.
7) Check that the account was authorized successfully and click save.
8) You will now see bit.ly in your list of Short Links. Select bit.ly as the Default if you wish.
Your default shortener will automatically be selected when you create new routes. To add bit.ly to your existing routes, click the pen icon under Actions in the bit.ly line item, choose "Apply this shortener to all existing routes" and click save account.