To access a register, use "<register>. You can then use then follow that with a command, e.g. to paste from a register use "<register>p.
You can also append to a register using a capital letter.
<c-r> (CTRL + R) can be used to insert from a register while in insert mode.
View all registers using :reg
Some useful registers:
0-9 - numbered registers for the latest yank
" - unnamed register, last delete or yank
* - clipboard
+ - clipboard (linux)
. - last inserted text
% - current file path
: - most recently executed command (how [[202512231254130-vim-repeat]] works)
/ - last search