You can use the following function to read a txt file.
readmatrix, readtable, load etc
Please refer the MATLAB Docs to read about different functions.
>> whos data
Name Size Bytes Class Attributes
data 1040x1393 11589760 double
Please ensure that the text file in the proper arrangement and alignment of all data elements. You may need to avoid 2 or 3 lines to avoid any headers associated with the file.
Notice the large number of dots in the image. All about how you represent the data (data type)