There are many ways, some of which depend on the context. If you are talking about here on gamesquad, the easiest way is to underline a less-than "<", e.g. "<". You can also insert a true less-than-or-equal unicode character. The less-than-or-equal-to is unicode character U+2264 (unicode characters are numbered starting at at zero, with the "U+" just indicating that the thing that follows is a (hexadecimal) unicode character code), so on my computer (debian linux) I hit ctrl-shift-u, 2264, <space>, "≤", to get a true unicode less-than-or-equal (which has a slightly different appearance (in my font anyway) than the underlined less-than. The method for inserting a unicode character may be different on your OS. There are also "special character picker windows", but those will be OS- and sometimes program-dependent (e.g. I believe MS Word has a special character picker in the menu somewhere). If you are writing HTML, the sequences "≤" or "≤" or "≤" will work.
JR