For the value on line 171 on T5013 there a 3 choices in turbotax where I can place this: investment, rental, cap gains, how do i know which 171 box to enter my value in?

Your advisor or issuer of the T5013 Statement of Partnership Income will usually supply an information package with details as to what types of income have been reported on the statement. From this information, you should be able to determine what your Foreign Tax reported in Box 171 was paid on.