Logging in to my remote desktop - I formerly could click on a Ctl/Alt/Delete button but can't find i

When TV first connects my desktop computer to my remote desktop computer, I used to log-on by clicking on a Ctl/Alt/Delete button at the top of the screen of my remote computer..  Now, that button has disappeared and I can't get logged on.  I may have changed a setting inadvertantly on my remote desktop computer.  Any way to get that Ctl/Alt/Delete button back?  I'm locked out of my remote desktop!  I use Windows 10 on both computers.