Posting a mezuzah

Posting a mezuzah on your doorframes is an explicit biblical commandment

A mezuzah is normally posted on the right doorpost (as you enter) of any house or room where Jews dwell (excluding bathrooms), at the beginning of the upper 1/3 of its height. The top should point diagonally toward the inside.

Metal surface
Clean and dry the surface intended for the mezuzah and the back of the mezuzah and attach the mezuzah to the door frame using a light coat of epoxy glue. The mezuzah can instead be fixed to a small wood board and then attached to the board to the doorframe.

Wooden surface
Attach the mezuzah to the doorframe using nails or screws (suggested) avoiding to scratch its surface.

Blessing (Brachah)
When posting a mezuzah on your doorframe, you say the following Hebrew blessing:

Ba-ruch a-tah A-do-nai
E-lo-hei-nu me-lech ha-o-lam,
a-sher kid-sha-nu b'mitz-vo-tav
v'tsi-va-nu lik-bo-a m'zu-zah

The blessing takes this form, since affixing a mezuzah is an explicit biblical commandment.