This is what your menu lines should look like I added one line for testing, you must copy and paste the code to notepad and save Blkins.lsp to a supported Autocad path, or else edit the (Load "c:\\yourdirectory\\your path\\etc\\Blkins") to suit, you can give it any name you like, just match. So pick "Load blocks" only need to do once.
***MENUGROUP=STRUCTURAL_STEEL
***POP12
**CTOPopSTRUCTURAL_STEEL
[Structural Steel]
[load blocks]^c^c(load "blkins")
[->UB]
[610UB125Test]^C^C(blkins "UniversalBeams_610UB125")
[610UB125]^C^C-INSERT UniversalBeams_610UB125;scale;1;
[610UB113]^C^C-INSERT UniversalBeams_610UB113;scale;1;
[610UB101]^C^C-INSERT UniversalBeams_610UB101;scale;1;
[->UC]
[310UC158]^C^C-INSERT UniversalColumns_310UC158;scale;1;
[310UC137]^C^C-INSERT UniversalColumns_310UC137;scale;1;
[310UC118]^C^C-INSERT UniversalColumns_310UC118;scale;1;
[310UC96.8]^C^C-INSERT UniversalColumns_310UC96.8;scale;1;
Blkins.lsp