this sentence is poorly written but this is what it means

legalese expressions

In my view, this requires a rewording, which could be along the lines I suggest. I agree the source text is not sparklingly written, but the meaning appears clear. The 'fideicomitente' is the Trustor, the person establishing the Trust. (The 'fideicomisario' would be the trustee.)

http://www.wilmingtontrust.com/repositories/wtc_sitecontent/... : "WHEREAS, Trustor desires to establish a trust of the property described in the attached “Schedule A” and other property which may be added from time to time, all of which is hereafter called the “trust fund;”..."

http://www.town.dennis.ma.us/Pages/DennisMA_BComm/maht/maht.... : "In accordance with the provisions of MGL c. 44 ... , the Town of Dennis hereby establishes a trust to be known as the 'Dennis Affordable Housing Trust Fund' (the 'Trust'). ..."

Regarding the second part, language in which the trustee agrees to be bound by the terms of a trust is much more common, since the trustor is entrusting the trustee with the property; but certainly a trust agreement is bilateral and it makes sense for trustor to accept the terms as well. Here's an example of such language:

http://www.sec.gov/Archives/edgar/data/1382134/0001144204100... : "Now, therefore, in consideration of the above Recitals, and other good and valuable consideration, ... Trustor hereby agrees to be bound by, and further supplement and modify the Trust Deed with the following provisions ..."

Your message brought to light the situation with respect to the context. Following this, there is a term in Spanish akin to "to join", that is "asociarse". From there the first term suggested. The second term was a bit different and was found to be "conform with"/pursuant to. Hope this fits the terms sought.

of course it means to join into, Asker is quite correct