That just means that the cartomizer that they include with the tank has an ohm rating of 1.5 ohm. You can put any cartomizer in the tank that you wish.
Having said that, tanks and cartomizers come in two basic lengths.
Standard size tanks match up with standard size cartomizers (35mm length cartos, ie Boge, Ikenvape standard, etc).
XL tanks match up with XL length cartomizers (45mm length cartomizers, ie Smokteck dual and single coils, Boge XL, Ikenvape Mega, etc) So, in essence, either match your tank length with the appropriate cartomizer, or if you already have a favorite cartomizer match a tank length to it.
DCT stands for dual coil tank. It doesn't mean it can not accept a single coil cartomizer. It's the same analogy as Q-tips for cotton swabs, Band Aid for elastic bandage, etc. DCT tanks match with an XL 45mm cartomizer.

XL tank and standard size tanks from IBTanked.
There are pro's and con's to using dual coil cartomizers vs single coil cartomizers. Mostly it is preference. Do realize that dual coil cartos will drain your batteries faster than single coils will.
I generally recommend that new carto tank users buy pre-punched cartos for their tanks. This will remove one of the human error issues that can occur when beginners try to punch their own cartos.
I have a listing of several vendors that sell single coil pre-punched cartos in my blog entries under my avatar.
I recommend watching the following video demo to learn the basics of carto tanking: