Transferred where? To the 401k plan of your new employer? To an IRA?
If the transfer is to an IRA, you were talking to the wrong people when you went to the HR/401k people at your previous employer. Most (more likely all) IRA custodians would love to get their hands on that money to invest it for you. What you need to do is go to your current
IRA custodian's website, tell them you want to roll over your 401k into your current IRA, give them all the information, and effectively say,
"Go get 'em, Bears!" and they will do all the work for you. (In fact, IRA custodians typically have links to click on that will walk you through the entire process). Don't have a current IRA? Pick a custodian (say someone like Rearguard or Churlish Swab), tell them you want to open a new IRA and want to fund it via rollover from your 401k and sit back and relax; they will take care of it all for you.
Transferring to the 401k plan of your current employer is a little more complicated because not all 401k plans allow transfers into the plan. Again, talk to the HR/401k plan people of your current employer first
to find out what is needed. It might be that your ex-employer's plan
will cut a check payable to the new trustee and send it to you to
send on to the new trustee, rather than send the money directly to
your new 401k plan as is
common in trustee-to-trustee transfers. You can't cash the check
since it is not payable to you, but it is your responsibility to
ensure that it gets to the right place. Whether rolling over
your 401k funds into the plan of a new employer is a good idea
or a bad idea depends on lots of factors. I have discussed
some of these factors in
this answer to a related question.