I love these historical instruments and was told I could place them in Logic. I thought I should ask guidance before I try so as not to destroy what I have now.
I'm new to Logic but is seemed tp work well with a musical i had to record this past year.
Thank you for any help!
Eric

Assuming when you mention Logic, you mean Logic Pro X, create a new AU (Audio Units) instrument.  Then follow the drop-down windows to select Modartt, and then the appropriate version of Pianoteq (such as Pianoteq 6 or Pianoteq 7 as required).  Once you have created a Pianoteq Audio Unit instrument, it is a simple matter of selecting the historic piano model you wish to use. 

Hope this helps,

Cheers,
Joe