I bought a smith corona SD770 at a garage sale I have found correction tape for it BUT when I set it on the spolls and put the ribbon cartridge back on and type the correction tape comes up I don't kn

The correction tape is two spools it installs on the left side below the ribbon and the right side below the ribbon.

lift the top remove the black ribbon then you can see the lift off tape it should lift up then install the new cartridge.

you have to turn the spool with the knob untill there is tension on the tape or it won't stay in place

Do they try to lift? Try taking off the corr tape, then hit correct and see if arms lift. If they do, try a different corr tape. Sometimes they bind up.

Where can I locate instruction on how to install the correction ribbon on a Smith Corona electric typewriter?

I found a manual for a different model Smith corona which may help. Is sounds like the correction cartridge needs to go in first. Here is the link to the manual and best of luck to you.
http://www.smithcorona.com/pdf/Office2000/Office2000Chap7.pdf

Be sure that the correction tape is a dry type general ribbon # T355 or equivelent.

DickyO

Be sure that you have a dry L/O tape Gen. Ribb. # t355 or equivwlent if you are using a tacky ribbon it will give you fits.

DickyO

sounds like the corr tape doesn't have the proper tension on it. turn wheel on corr tape cartridge, or if there isn't a wheel, some don't, there is a little lever to the left and under the left side where the cart. fits down. push this until the arm on the right side moves to the left