Before saving the template file TurboCAD must be running as administrator so right click on the TurboCAD icon and choose Run As Administrator. Then set up your template the way you want from your already existing drawing that has all your styles in it. Then click File-> Save As and change the file type to .tct, save the file to the location given below:

If 64 bit

C:\Program Files\IMSIDesign\(TurboCAD Version)\Template

If 32 bit

C:\Program Files(x86)\IMSIDesign\TC(TurboCAD Version)\Template

After you do this to open the template and start drawing in it you can just go to File-> New-> New From Template and choose the Template by its name.

If you ever add new styles while using the template just re save the empty template using the same process after you save the drawing file first.