Merge pull request #77 from mmikeww/patch-6

instructions to Sign on Coldcard via SD Card

Author: mflaxman

_pages/send-bitcoin/advanced.md

@@ -10,9 +10,15 @@ Fortunately, your wallet software will abstract this away for you.
 [TODO]: add link with more details explaining this.
 
 #### Sign on Coldcard via SD Card
-SD Card is a better airgap.
-
-TODO: add instructions
+SD Card is a better airgap, and preferable over signing through USB.
+
+1. On the previous page, at Step 9, choose "Sign with SD Card file" instead of choosing "Sign with USB"
+2. Click Save transaction, and save to your SD card
+3. Eject the SD card from computer, and load into Coldcard
+4. Click "Ready to sign" on Coldcard and confirm transaction details
+5. Coldcard will save the signed transaction back to the SD card, but with the `-part` suffix at the end of the filename
+6. Back in Specter, click "Load transaction from file", and choose the file on the SD card with the `part` suffix
+7. Broadcast 
 
 
 #### Inspect Signed Transactions Before Broadcasting