Use the publisher's patch instructions

Saikey's general instructions say to install the Steam game, confirm its language, extract the patch, and run the publisher's .exe. Select the same language as Steam, accept the license, choose or confirm the game folder, and install. Saikey says the next launch should show “(Steam Patched Version)” in the window title when the process succeeds. These are general publisher steps; confirm the live Stranded with You package and build notes before installing.

Confirm the package before installing

The official instructions explain the general process, but the exact current Stranded with You package, version, and supported build still need to be checked on Saikey's live product and patch pages. Do not assume a Demo patch is compatible with the retail Steam build, or vice versa.