をこめて, or
を込（こ）めて when appearing in its kanji form, is a phrase that expresses when something is ‘full of (A)’, or ‘filled with (A)’. The structure is comprised of を, and the て-form of the る-Verb 込（こ）める, which means ‘to pack into’, or ‘to load with’. In this way, the literal meaning is fairly consistent with the standard English translations.
をこめて will appear directly after the noun expressing the particular feeling or emotion being discussed.
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感謝（かんしゃ）の気持（きも）ちを込（こ）めて、1年間（ねんかん）お世話（せわ）になった先生（せんせい）に花束（はなたば）をあげた。
Full of the feeling of gratitude, I gave a bouquet of flowers to a teacher who has taken care of me for the past year.
夫（おっと）は毎晩（まいばん）、愛（あい）を込（こ）めて晩御飯（ばんごはん）を作（つく）ってくれる。
My husband cooks dinner every night with love.
歌（うた）うのが下手（へた）でも、心（こころ）を込（こ）めて歌（うた）えば上手（じょうず）に聞（き）こえる。
Even if you are not a good singer, you can sound like a good singer if you sing with all your heart.
Caution - It is important to note that this particular structure is treated as a set phrase, and will primarily only be used when some particular feeling or emotion is the thing that is being ‘packed into (A)’.