I just said that it is not a good practice as some people reported damaged backup files.
Personally I do not see a problem with it and technical issues related to such usage.
I use my TC as both: backup for a coupke of computers and archive file storage - never had a problem and I have ran a couple of restores.
You do not say what laptop you have.
Guessing a Mac, once you have your TC set properly for backup you should see your TC in Finder Window under Shared and its name (whatever you call it).
Just click on it, authenticate if you password protected it and you will have access to the drive.
You can create folders in there.
Just make sure you do not touch the sparsebundle files which are the Time Machine backups.