To keep it short and simple

1. Open the Framemaker document.
In an ideal case, the document was prepared with CAT translation in mind and no special editing is needed.
Usually this is not the case and several workarounds will improve later work in Tageditor. If you are not familiar with work in Framemaker, proceed to next step (2), as these are not necessary, require at least slightly advanced experience, and they just make the later translation more understandable.
a/ turn off the hyphenation for all styles used in document (in Paragraph designer)
b/ manualy move anchors of index entries and crossreferences to the begining or the end of sentences (this way yur links in tageditor will not be "poluted" by internal tags. Sometimes they appear in the middle of the word, which is unpleasant during the translation. It can also ruin your match.
c/manage conditional text. If you need to translate only one context, make it unconditional and delete other contexts - if you need to translate more contexts - rare situation - do not touch the conditions, but prepare to confusing work in tageditor.

2. Save the Framemaker document (.fm) as .mif
In "Save as" dialog choose .mif in the drop down for file type

Note:
If you have a FM7 file and want to process it in Trados 5.5 or lower, open the .mif file(s) in Wordpad and rewrite the first line
<MIFFile 7.00> # Generated by FrameMaker 7.x
to
<MIFFile 6.00> # Generated by FrameMaker 7.x
- little strange, but it works, since there is only a slight difference between miff 6 and 7 and this does not affect the part that is processed by trados for translation

3. Create project in Workspace

4. Add miff files to your project, preferably to separate component

5. Choose the component containing .mif files and select "convert to stf files" and click OK

6. If the conversion went OK (take care about the workaround for lower versions of trados mentioned in point 2), choose the component again and select "convert to Tradostag" and click OK.

7. Now you have your Tradostag files in folder "project folder/target_language_/Trados/Translated" e.g. "Proj04/German/Trados/Translated"

8. Translate the files that end with .rtf.ttx in Tageditor.
Take care of tags -could be a lot ofhtem in certain files. There are some you may omit, some you must preserve - but that is another topic. Leave the translated files in the same folder with the same name. (you can backup the untranslated somwhere else)

9. Open your project, choose the component with .mif files and select "convert Tradostag to original format" and click OK.

10. Choose the component again and select "convert STF files to original format" and click OK.
If the conversion fails - check the log - most probably you destoyed some essential tags - run S-tag verifier and repair the files - that is also another topic

11. You have translated .mif files in your target language folder

12. Open the .mif files in FrameMaker.
Some slight editing might be needed - depends on original file - check if the text does not overflow the frames.

13. Save files as .fm - and the thing is accomplished

Takes a lot of practise, so experiment yourself.

Peter