Are you looking for a particular compound for NMR? Or are you looking to get an NMR for a compound which shows activity, but you do not yet know its structure?
If looking for a compound previously isolated as per the first question, follow the purification procedure from the literature or the instruction in your lab.
If it is an unknown compound, you need to do assay directed fractionation to get the compound sufficiently pure to determine its structure.
Either way, the crude extract will need purification to get NMR data for the desired compound.
I agree with Doc Silver, You need to purify your sample first and load only a pure sample. Our work in the link below may give you an idea on the methods and choice to make on the selection of the methods.
You need to purify the plant sample if such a sample is not a pure sample. The purification processes involves fractionation and chromatography (vacuum liquid chromatography, sephadex separation and semi-preparative HPLC).