For the selected paragraphs:

Click in the paragraph, and then on the Paragraph palette (Type > Paragraph > Paragraph palette), on the Spc tab, under Word spacing, enter values in Min, Med and Max.

The specified values override the format-level settings.

For the current format:

Open a format for editing, and then click Paragraph.

On the Spc tab, under Word spacing, enter values in Min, Med and Max.

About Min, Med and Max values

The values are expressed in thousands of Em-space. The default value is set to typographical standard values of 260, 310 and 360 1/1000ths of Em-space.

The Min and Max values apply only when you’re setting justified type. For all other paragraph alignments, Fred4 uses the values you entered for Med. The more the Min and Max values differ from the Med value, the more latitude you give to Fred4 to increase or decrease spacing in justifying the line.

About Fred and InDesign differences on specifying word spacing

The InDesign values are based on 250 thousands of EM-space, while Fred values are based on 1 thousand of EM-space. Therefore, the InDesign's 75 corresponds to Fred's 187, InDesign's 90 corresponds to Fred's 225.

To calculate quickly, use the Excel spreadsheet expression with two fields: in the InDesign field enter the value as shown in the Justification dialog of InDesign, and the Fred field enter the expression:

Int(indesign_field/0.4)

Assuming the InDesign field is B1, and the Fred field is C1, the expression in C1 would be:

=Int(B1/0.4)