Definition From Wikipedia: A single-chain variable fragment (scFv) is not actually a fragment of an antibody, but instead is a fusion protein of the variable regions of the heavy (VH) and light chains (VL) of immunoglobulins, connected with a short linker peptide of ten to about 25 amino acids. The linker is usually rich in glycine for flexibility, as well as serine or threonine for solubility, and can either connect the N-terminus of the VH with the C-terminus of the VL, or vice versa. This protein retains the specificity of the original immunoglobulin, despite removal of the constant regions and the introduction of the linker. 

It is possible to create scFv structures from the target VL, linker and VH sequences using the Model Antibody Framework protocol in Discovery Studio. The process is the same as that in the tutorial ‘Creating a 3D model of an antibody Fv domain from a sequence’ found in the Help>Help Topics>Tutorials help pages. You will first need to find suitable template(s) and then build a structure based on the template(s). However in this case when running the Model Antibody Framework protocol you would expand the Advanced parameter and set Single Chain Model to True. You can then choose the Chain Order of heavy-light or light-heavy. The linker sequence should be included at the start or end of one of the input sequences depending on the Chain Order you use. For example, if you choose heavy-light the linker sequence can be at the end of the VH or beginning of the VL sequence.

Note the different ways you can specify templates in the highlighted section of the parameter Help above.