Well things I would suggest you check are this
1. on the config portion you have entered the correct database information where asked for xenforo.
2. on the config portion you entered the correct globalsalt where asked for
3. On step 4 where you select xenforo as your integration type you enter the correct xenforo mysql table prefix asked for.
Your errors suggest your database info or xenforo table prefix have not been entered correctly thus there are connection issues trying to run simple queries against your xenforo database.
You need to reinstall using the correct information.