If you want to get svn versions, you can use fpcupdeluxe.
Otherwise it will be best, if you have fpc already installed (it takes a bit to build it yourself....)
For current Lazarus from svn, you need at least fpc 3.0.2 or maybe 3.0.0 (not sure), I doubt it will run with any version before 3.0. (but not tested)
If you do have an existing (and working) previous version of the Lazarus executable (not to old), then you can copy that into the new sources, and use build from the tools menu.
Otherwise
make bigide OPT="....."
where ..... can be any fpc argument: -O2 -gh -gl -gw -godwarfsets -Criot and others.
Then start the IDE, add your packages (if needed) and rebuild.
Which weans, you can also do "make bigide" without options, and add the options when you rebuild from the IDE.
If you have the sources in your home dir (or writeable to your user) you do not need to do "make install". Just use the IDE from the build dir. That way you have all the sources in place.
https://wiki.lazarus.freepascal.org/Installing_Lazarus---
If you have more than one build on your system:
https://wiki.lazarus.freepascal.org/Multiple_Lazarus#Using_lazarus.cfg_file