翻訳 - 日本語-英語 - 幸せがありたいと思いなさい

Romanized: "Shiawase ga aritai to omoi-nasai"
First off, this is incorrect Japanese, and was not produced by a native speaker.
I asked my friend (a fellow university professor, and a native Japanese) if this was possible in Japanese in any conceivable situation and he said definitely not.
Some possibilities for correcting it are as follows:
Shiawase DE ITAI to omoinasai
Shiawase NI NARITAI to omoinasai
Shiawase GA ATTE HOSHII to omoinasai
In the same order, they would be translated as:
Please think "I want to be (as) happy (as I am now)."
Please think "I want to be happy (in the future)."
Please wish for happiness. (lit: Please think "I wish there were happiness.")
Cultural note: the "omoi-nasai"-style imperative form of the verb (lit: "deign to think") is kind of "between" our command form "Think..." and request form "Please think.."
A straight-up command form in Japanese would be
"...to omotte" (= "Think...")
and a softer request would be
"...to omotte kudasai" (= "Please think...")
Because the "omoi-nasai" is between them, it could be translated either as a "rough request" or a "soft command," depending on the context...
It's interesting to note that it's often the preferred command form for women; with men usually preferring to use the "rougher" command forms...
That's probably more than anyone cares to know, but...
:)
For what it's worth...